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We come in contact with toxic substances every day. After reviewing the material in this unit, share with the class what you think are the two or three potentially most toxic substances that can enter our everyday lives. Do you think that the Occupational Safety and Health Administration (OSHA), the Environmental Protection Agency (EPA), the Consumer Product Safety Commission (CPSC), and/or businesses are doing enough to limit these potential exposures? Why, or why not?

Unit Assessment

QUESTION 1

A press area of a plant has six 400-ton presses in operation 24 hours a day, 7 days a week. Personal monitoring using noise dosimeters has shown that 8-hour time-weighted average (TWA) exposures range from 92.0 dBA to 94.5 dBA.
Using OSHA’s Hierarchy of Controls, write a hazard scenario using the information above that summarizes your approach to reducing the risks associated with the hazard. Indicate which type of hazard control you will use and describe exactly how it will be used to control the hazard. 
Your response must be at least 200 words in length.

QUESTION 2

A plant that manufactures automobile chassis includes a production area containing 100 robotic welding stations. An adjacent area contains 10 welding booths where employees perform hand welding using MIG welders to rework welds that have been identified as unacceptable. Personal air sampling shows that personal exposures at 5 of the welding booths located in the middle of the rework exceed the OSHA PEL for lead, nickel, and iron oxide fumes. On average, the personal exposures exceed the applicable OSHA PEL by 2-3 times.
Using OSHA’s Hierarchy of Controls, write one paragraph for the hazard scenario above that summarizes your approach to reducing the risks associated with the hazard. Indicate which type of hazard control you will use and describe exactly how it will be used to control the hazard.
Your response must be at least 200 words in length.

QUESTION 3

Employees in the paint department of an automotive parts production facility use styrene to clean residue off the parts as they come off the paint line. The OSHA PEL for styrene is 100 ppm as an 8-hour TWA exposure. Personal air samples show that during peak production times, exposures range from 150 ppm to 200 ppm for an 8-hour shift. The parts cleaning is performed in a small room with one door.
Using OSHA’s Hierarchy of Controls, write one paragraph for the hazard scenario above that summarizes your approach to reducing the risks associated with the hazard. Indicate which type of hazard control you will use and describe exactly how it will be used to control the hazard. 
Your response must be at least 200 words in length.

QUESTION 4

A plant has an operation that produces automotive headliners in a press. The process uses a compound that contains methylene bisphenyl isocyanate (MDI). The compound containing MDI must be used in the production process to meet the client’s specifications for the headliner. The OSHA PEL for MDI is 0.02 ppm as a ceiling concentration. Personal air samples collected for 15 minutes at the time when the press opens show that short-term exposures range from 0.02 ppm to 0.06 ppm. 
Using OSHA’s Hierarchy of Controls, write one paragraph for the hazard scenario above that summarizes your approach to reducing the risks associated with the hazard. Indicate which type of hazard control you will use and describe exactly how it will be used to control the hazard.
Your response must be at least 200 words in length.

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Controlling Exposure
The following references aid in controlling workplace hazards
associated with chemical hazards and toxic substances.

Overview of Controls

Controlling exposures to chemical hazards and toxic substances is the
fundamental method of protecting workers. A hierarchy of controls is
used as a means of determining how to implement feasible and
effective controls.

OSHA’s longstanding policy is that engineering and work practice
controls must be the primary means used to reduce employee
exposure to toxic chemicals, as far as feasible, and that respiratory protection is required to be used when engineering or
work practice controls are infeasible or while they are being implemented.

Where possible, elimination or substitution is the most desirable followed by engineering controls. Administrative or work
practice controls may be appropriate in some cases where engineering controls cannot be implemented or when different
procedures are needed after implementation of the new engineering controls. Personal protection equipment is the least
desirable but may still be effective.

Type of Control Examples

Elimination/Substitution Substitute with safer alternatives. [See
Transitioning to Safer Chemicals: A Toolkit for
Employers and Workers]

Engineering Controls (implement physical change to the
workplace, which eliminates/reduces the hazard on the
job/task)

Change process to minimize contact with
hazardous chemicals.
Isolate or enclose the process.
Use of wet methods to reduce generation of dusts
or other particulates.
General dilution ventilation.
Use fume hoods.

Administrative and Work Practice Controls (establish
efficient processes or procedures)

Rotate job assignments.
Adjust work schedules so that workers are not
overexposed to a hazardous chemical.

Personal Protective Equipment (use protection to
reduce exposure to risk factors)

Use chemical protective clothing.
Wear respiratory protection. [See the Respiratory

Safety and Health Topics /

Chemical Hazards and Toxic Substances

Chemical Hazards and Toxic Substances

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Protection Safety and Health Topics page]
Use gloves.
Wear eye protection.

Additional Information

Permissible Exposure Limits – Annotated Tables. OSHA, (2013). OSHA has annotated the existing Z-Tables with other
selected occupational exposure limits. OSHA has chosen to present a side-by-side table with the Cal/OSHA PELs, the
NIOSH Recommended Exposure Limits (RELs) and the ACGIH® TLVs®s which provides employers, workers, and
other interested parties a list of alternate occupational exposure limits that may serve to better protect workers.
Hazard Communication. OSHA Safety and Health Topics Page. Provides example HazCom programs, many training
resources, as well as links to the proposed Globally Harmonized System of Classification and Labeling of Chemicals
(GHS).
Hazard Communication: Small Entity Compliance Guide for Employers That Use Hazardous Chemicals. OSHA
Publication 3695, (2014).
Process Safety Management. OSHA Safety and Health Topics Page. Contains requirements for the management of
hazards associated with processes using highly hazardous chemicals included in the Process Safety Management of
Highly Hazardous Chemicals Standard (29 CFR 1910.119).
Sampling and Analysis. OSHA Safety and Health Topics Page. Describes chemical sampling and analysis used by
occupational and safety professionals to assess workplace contaminants and associated worker exposures.
Chemical Safety. National Institute for Occupational Safety and Health (NIOSH) Workplace Safety and Health Topic.
Provides information on many hazardous chemicals and chemical concerns.
Recommendations for Chemical Protective Clothing: A Companion to the NIOSH Pocket Guide to Chemical Hazards.
National Institute for Occupational Safety and Health (NIOSH). Identifies protective clothing materials appropriate for
chemicals listed in this pocket guide.
A Guide for Evaluating the Performance of Chemical Protective Clothing. U.S. Department of Health and Human
Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 90-109, (June 1990).
Includes selection and evaluation guidelines for protective clothing.
Report To Congress On Workers’ Home Contamination Study Conducted Under The Workers’ Family Protection Act
(29 U.S.C. 671a). U.S. Department of Health and Human Services (DHHS), National Institute for Occupational Safety
and Health (NIOSH), (September 1995). Summarizes the hazards to which a worker’s family may be exposed.

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Section III: Chapter 3

Ventilation Investigation

Table of Contents:

I. Introduction

II. Health Effects

III. Standards and Codes

IV. Investigation Guidelines

V. Prevention and Control

VI. Bibliography

List of Appendices:

Appendix III:3-1. Ventilation Primer

Appendix III:3-2. Glossary

Appendix III:3-3. OSHA and Consensus Standards

Appendix III:3-4. Troubleshooting an Exhaust System–Some Helpful Hints

For problems with accessibility in using figures and illustrations in this document, please contact the Office of Science and Technology Assessment at (202)
693-2095.

I. Introduction

Industrial ventilation generally involves the use of supply and exhaust ventilation to control emissions, exposures, and chemical hazards in the workplace.
Traditionally, nonindustrial ventilation systems commonly known as heating, ventilating, and air-conditioning (HVAC) systems were built to control temperature,
humidity, and odors.

A. Ventilation may be deficient in:

confined spaces;
facilities failing to provide adequate maintenance of ventilation equipment;
facilities operated to maximize energy conservation;
windowless areas; an

d

areas with high occupant densities.

Any ventilation deficiency must be verified by measurement.

B. There are five basic types of ventilation systems:

1. dilution and removal by general exhaust;
2. local exhaust (see Figure III:3-1);

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Figure III:3-1. Components of a Local Exhaust System

3. makeup air (or replacement);
4. HVAC (primarily for comfort); and
5. recirculation systems.

C. Ventilation systems generally involve a combination of these types of systems.

For example, a large local exhaust system may also serve as a dilution system, and the HVAC system may serve as a makeup air system (see Appendix III:3-1 for
a primer and Appendix III:3-2 for an explanation of these terms).

II. Health Effects

Inadequate or improper ventilation is the cause of about half of all indoor air quality (IAQ) problems in nonindustrial workplaces (see Section III, Chapter 2, Indoor
Air Quality). This section of the manual addresses ventilation in commercial buildings and industrial facilities.

A. Indoor Air Contaminants

Indoor Air Contaminants include but are not limited to particulates, pollen, microbial agents, and organic toxins. These can be transported by the ventilation
system or originate in the following parts of the ventilation system:

wet filters;
wet insulation;
wet undercoil pans;
cooling towers; and
evaporative humidifiers.

People exposed to these agents may develop signs and symptoms related to “humidifier fever,” “humidifier lung,” or “air conditioner lung.” In some cases, indoor
air quality contaminants cause clinically identifiable conditions such as occupational asthma, reversible airway disease, and hypersensitivity pneumonitis.

B. Volatile Organic and Reactive Chemicals

Volatile Organic and Reactive Chemicals (for example, formaldehyde) often contribute to indoor air contamination. The facility’s ventilation system may transport
reactive chemicals from a source area to other parts of the building. Tobacco smoke contains a number of organic and reactive chemicals and is often carried this
way. In some instances the contaminant source may be the outside air. Outside air for ventilation or makeup air for exhaust systems may bring contaminants into
the workplace (e.g., vehicle exhaust, fugitive emissions from a neighboring smelter).

See Section III, Chapter 2, Indoor Air Quality, for a discussion of common indoor-air contaminants and their biological effects.

III. Standards and Codes

A. Consensus Standards

Appendix III:3-3 is a compilation of OSHA and industry consensus standards. Foremost are those recommended by the Air Movement and Control Association
(AMCA), the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), the American National Standards Institute (ANSI), the Sheet
Metal and Air Conditioning Contractors National Association (SMACNA), the National Fire Protection Association (NFPA), and the American Conference of
Governmental Industrial Hygienists (ACGIH). AMCA is a trade association that has developed standards and testing procedures for fans. ASHRAE is a society of
heating and air conditioning engineers that has produced, through consensus, a number of standards related to indoor air quality, filter performance and testing,
and HVAC systems. ANSI has produced several important standards on ventilation, including ventilation for paintspray booths, grinding exhaust hoods, and open-
surface tank exhausts. Four ANSI standards were adopted by OSHA in 1971 and are codified in 29 CFR 1910.94; these standards continue to be important as
guides to design. ANSI has recently published a new standard for laboratory ventilation (ANSI Z9.5). SMACNA is an association representing sheet metal
contractors and suppliers. It sets standards for ducts and duct installation. NFPA has produced a number of recommendations (which become requirements when
adopted by local fire agencies), e.g., NFPA 45 lists a number of ventilation requirements for laboratory fume hood use. The ACGIH has published widely used
guidelines for industrial ventilation.

B. OSHA Regulations

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Table III:3-1. Common Ventilation Conditions and Causes

Condition Possible cause(s)

Worker complaints, improper use of
system, nonuse of system, alteration of
system by employees.

The hood interferes with work
The hood provides poor control of contaminants.

Excessive employee exposures althoug

h

flow volumes and capture velocities are
at design levels.

Employee work practices need improvement.
The ventilation system interferes with work or worker productivity and leads workers to
bypass the system.
Employee training is not adequate.
Design of system is poor.

Constant plugging of duct. Plugged ducts occur when transport velocity is inadequate or when vapor condenses in
the duct, wets particles, and causes a build-up of materials.
These problems are caused by poor design, open access doors close to the fan, fan
problems, or other problems.

Reduced capture velocities or excessive
fugitive emissions.

The cause of these conditions is usually reduced flow rate, unless the process itself has
changed.
Reduced flow rate occurs in the following situations:

plugged or dented ducts
slipping fan belts
open access doors
holes in ducts, elbows
closed blast gate to branch, or opened blast gates to other branches, or corroded and
stuck blast gates
fan turning in reverse direction (This can occur when lead wires are reversed and
cause the motor and fan to turn backwards. Centrifugal fans turning backwards may
deliver up to only 50% of rated capacity.)
worn out fan blades
additional branches or hoods added to system since initial installation, or
clogged air cleaner.

Table III:3-2. Problem Characterization

Emission source
Where are all emission sources or potential emission sources located?
Which emission sources actually contribute to exposure?
What is the relative contribution of each source to exposure?
Characterization of each contributor:

chemical composition

Ventilation criteria or standards are included in OSHA regulatory codes for job- or task-specific worker protection (see Appendix III:3-3). In addition, many OSHA
health standards include ventilation requirements. The four standards in 29 CFR 1910.94 deal with local exhaust systems, and OSHA’s construction standards (29
CFR 1926) contain ventilation standards for welding. OSHA’s compliance policy regarding violation of ventilation standards is set forth in the Field Inspection
Reference Manual.

IV. Investigation Guidelines

A. Investigation Phases

Workplace investigations of ventilation systems may be initiated by worker complaints of possible overexposures to air contaminants, possible risk of fire or
explosion from flammable gas or vapor levels at or near the lower explosive limit (LEL), or indoor air quality complaints. The second phase of the investigation
involves an examination of the ventilation system’s physical and operating characteristics.

B. Faulty Ventilation Conditions and Causes

Common faulty ventilation conditions and their probable causes are listed in Table III:3-1. Specific points to consider during any investigation of a ventilation
system include emission source, air behavior, and employee involvement. Points that should be included in a review of operational efficacy are shown in Table III:3-
2. Appendix III:3-4 contains information on points to be checked in a troublesome exhaust system.

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temperature
rate of emission
direction of emission
initial emission velocity
pattern of emission (continuous or intermittent)
time intervals of emission
mass of emitted material

Air behavior
Air temperature
Air movement (direction, velocity)
Mixing potential
Supply and return flow conditions, to include pressure differences between space and surrounding areas
Sources of tempered and untempered make-up air
Air changes per hour
Influence of existing HVAC systems
Effects of wind speed and direction
Effects of weather and season

Employee
Worker interaction with emission source
Worker exposure levels
Worker location
Worker education, training, cooperation

C. Basic Testing Equipment

Basic testing equipment might include:

smoke tubes
velometers, anemometers:

swinging vane anemometer
thermal or hot-wire anemometer

pressure-sensing devices:
U-tube or electronic manometers
Pitot tube
thermal (thermal and swinging vane instruments measure static pressure indirectly)
aneroid (“bellows”) gauges

noise-monitoring equipment
measuring tapes
other: rags, flashlight, mirror, tachometer
combustible gas meter or oxygen meter
tubes for CO, CO , formaldehyde, etc.

D. Documentation

The characteristics of the ventilation system that must be documented during an investigation include equipment operability, physical measurements of the system,
and use practices.

E. Equipment Operability

Before taking velocity or pressure measurements, note and record the operating status of the equipment. For example, are filters loaded or clean? Are variable-
flow devices like dampers, variable-frequency drives, or inlet vanes in use? Are make-up units operating? Are system blueprints available?

F. Measurements

1. Duct diameters are measured to calculate duct areas. Inside duct diameter is the most important measurement, but an outside measurement is often
sufficient for a sheet metal duct. To measure the duct, the tape should be thrown around the duct to obtain the duct circumference, and the number should be
divided by (3.142) to obtain the diameter of the duct.

2. Hood and duct dimensions can be estimated from plans, drawings, and specifications. Measurements can be made with measuring tape. If a duct is
constructed of 2½ or 4-foot sections, the sections can be counted (elbows and tees should be included in the length).

2

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Figure III:3-2. Use of Smoke to Demonstrate Air Flow

Velocity = Distance/Time, or

V = D/T

Figure III:3-3. Use of Static Pressure Tap Into Duct to Measure Hood Static Pressure

3. Hood-face velocities outside the hood or at the hood face can be estimated with velometers, smoke tubes, and swinging-vane anemometers, all of which
are portable, reliable, and require no batteries.
a. The minimum velocity that can be read by an anemometer is 50 feet per minute (fpm). The meter should always be read in the upright position, and only

the tubing supplied with the equipment should be used.
b. Anemometers often cannot be used if the duct contains dust or mist because air must actually pass through the instrument for it to work. The instrument

requires periodic cleaning and calibration at least once per year. Hot-wire anemometers should not be used in airstreams containing aerosols.
c. Hood-face velocity measurement involves the following steps:

mark off imaginary areas;
measure velocity at center of each area; and
average all measured velocities.

d. Smoke is useful for measuring face velocity (see Figure III:3-2) because it is visible. Nothing convinces management and employees more quickly that the
ventilation is not functioning properly than to show smoke drifting away from the hood, escaping the hood, or traveling into the worker’s breathing zone.
Smoke can be used to provide a rough estimate of face velocity:

Squeeze off a quick burst of smoke. Time the smoke plume’s travel over a two-foot distance. Calculate the velocity in feet per minute. For example, if it
takes two seconds for the smoke to travel two feet, the velocity is 60 fpm.

4. Hood static pressures (SPH) should be measured about 4-6 duct diameters downstream in a straight section of the hood take-off duct. The measurement
can be made with a pitot tube or by a static pressure tap into the duct sheet metal (see Figure III:3-3)

a. Pressure gauges come in a number of varieties, the simplest being the U-tube manometer.
b. Inclined manometers offer greater accuracy and greater sensitivity at low pressures than U-tube manometers. However, manometers rarely can be used

for velocities less than 800 fpm (i.e. velocity pressures less than 0.05″ w.g.). Aneroid-type manometers use a calibrated bellows to measure pressures.
They are easy to read and portable but require regular calibration and maintenance.

5. Duct velocity measurements may be made directly (with velometers and anemometers) or indirectly (with manometers and pitot tubes) using duct velocity
pressure.
a. Air flow in industrial ventilation ducts is almost always turbulent, with a small, nonmoving boundary layer at the surface of the duct.
b. Because velocity varies with distance from the edge of the duct, a single measurement may not be sufficient. However, if the measurement is taken in a

straight length of round duct, 4-6 diameters downstream and 2-3 diameters upstream from obstructions or directional changes, then the average velocity
can be estimated at 90% of the centerline velocity. (The average velocity pressure is about 81% of centerline velocity pressure.)

c. A more accurate method is the traverse method, which involves taking six or ten measurements on each of two or three passes across the duct, 90° or
60° opposed. Measurements are made in the center of concentric circles of equal area.

d. Density corrections (e.g., temperature) for instrument use should be made in accordance with the manufacturer’s instrument instruction manual and
calculation/correction formulas.

6. Air cleaner and fan condition measurements can be made with a pitot tube and manometer.

G. Good Practices

1. Hood placement must be close to the emission source to be effective. Maximum distance from the emission source should not exceed 1.5 duct diameters.
a. The approximate relationship of capture velocity (V ) to duct velocity (V ) for a simple plain or narrow flanged hood is illustrated in Figure III:3-4. For

example, if an emission source is one duct diameter in front of the hood and the duct velocity (V ) = 3,000 feet per minute (fpm), then the expected
capture velocity (V ) is 300 fpm. At two duct diameters from the hood opening, capture velocity decreases by a factor of 10, to 30 fpm.

c d

d
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Figure III:3-4. Relationship of Capture Velocity (V ) to Duct Velocity (V )

Figure III:3-5. Rule of Thumb for Simple Capture Hoods: Maximum Capture Distance Should Not Be More

Than 1.5 Times the Duct Diameter

Figure III:3-6. Effective Flange Width (W)

Figure III:3-7. An Illustration of the Six-and-Three Rule

Figure III:3-8. Minimum Stack Height in Relation to Immediate Roof Line or Center of Any Air Intake on the Same

Roof

b. Figure III:3-5 shows a rule of thumb that can be used with simple capture hoods. If the duct diameter (D) is 6 inches, then the maximum distance of the
emission source from the hood should not exceed 9 in. Similarly, the minimum capture velocity should not be less than 50 fpm.

c. Figure III:3-6 provides a guide for determining an effective flange width.

2. System effect loss, which occurs at the fan, can be avoided if the necessary ductwork is in place.
a. Use of the six-and-three rule ensures better design by providing for a minimum loss at six diameters of straight duct at the fan inlet and a minimum loss at

three diameters of straight duct at the fan outlet (Figure II:3-7).

b. System effect loss is significant if any elbows are connected to the fan at inlet or outlet. For each 2½ diameters of straight duct between the fan inlet and
any elbow, CFM loss will be 20%.

3. Stack height should be 10 ft higher than any roof line or air intake located within 50 ft of the stack (Figure III:3-8). For example, a stack placed 30 ft away
from an air intake should be at least 10 ft higher than the center of the intake.

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Table III:3-3. Good Practices For Reviewing Plans and Specifications

Investigate the background and objectives of the project.
Understand the scope of the project. What is to be included and why?
Look for conciseness and precision. Mark ambiguous phrases, “legalese,” and repetition.
Do the specifications spell out exactly what is wanted? What is expected?
Do plans and specifications adhere to appropriate codes, standards, requirements,policies, and
do they recommend good practice as established by the industry?
Will the designer be able to design, or the contractor to build, the system from the plans and
specifications?
Will the project meet OSHA requirements if it is built as proposed?

PUT IT ON
PAPER

4. Ventilation system drawings and specifications usually follow standard forms and symbols, e.g., as described in the Uniform Construction Index (UCI).
a. Plan sections include electrical, plumbing, structural, or mechanical drawings (UCI, Section 15). The drawings come in several views: plan (top), elevation

(side and front), isometric, or section.
b. Elevations (side and front views) give the most detail. An isometric drawing is one that illustrates the system in three dimensions. A sectional drawing

provides duct or component detail by showing a cross-section of the component.
c. Drawings are usually drawn to scale. (Check dimensions and lengths with a ruler or a scale to be sure that this is the case. For example, ⅛ inch on the

sheet may represent one foot on the ground.) Good practices to follow when reviewing plans and specifications are listed in Table III:3-3.

V. Prevention and Control

A well-designed system and a continuing preventive maintenance program are key elements in the prevention and control of ventilation system problems.

A. Elements of a Good Maintenance Program

1. Establish a safe place to file drawings, specifications, fan curves, operating instructions, and other papers generated during design,
construction, and testing.

2. Establish a program of periodic inspection
a. The types and frequencies of inspections depend on the operation of the system and other factors.

Daily: Visual inspection of hoods, ductwork, access and clean-out doors, blast gate positions, hood static pressure, pressure drop across air cleaner,
and verbal contact with users. (“How is the system performing today?”)
Weekly: Air cleaner capacity, fan housing, pulley belts.
Monthly: Air cleaner components.

b. A quick way to check for settled material in a duct is to take a broomstick and tap the underside of all horizontal ducts. If the tapping produces a “clean”
sheet metal sound, the duct is clear. If the tapping produces heavy, thudding sounds and no sheet metal vibration, liquids or settled dust may be in the
duct.

3. Establish a preventive maintenance program. Certain elements of any ventilation system should be checked on a regular schedule and replaced if found
to be defective.

4. Provide worker training. Workers need to be trained in the purpose and functions of the ventilation system. For example, they need to know how to work
safely and how best to utilize the ventilation system. Exhaust hoods do little good if the welder does not know that the hood must be positioned close to the
work.

5. Keep written records. Maintain written documentation not only of original installations but also of all modifications as well as problems and their resolution.

B. Dealing With Micro-Organisms

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Table III:3-4. Preventive Measures for Reducing Microbial Problems in Buildings

Prevent buildup of moisture in occupied spaces (relative humidity of 60% or less).
Prevent moisture collection in HVAC components.
Remove stagnant water and slime from mechanical equipment.
Use steam for humidifying.
Avoid use of water sprays in HVAC systems.
Use filters with a 50-70% collection efficiency rating.
Find and discard microbe-damaged furnishings and equipment.
Provide regular preventive maintenance.

If you suspect microbial agents, check for stagnant water in the ventilation system. The presence of mold or slime is a possible sign of trouble. Table III:3-4 lists
preventive measures for controlling microbial problems in ventilation systems.

C. Volatile Organic or Reactive Chemicals

If an organic or reactive chemical (e.g., formaldehyde) is believed to be the primary agent in an IAQ problem, potential controls to consider include additional
dilution ventilation, removal or isolation of the offending material, and the transfer of sensitized employees.

D. Tobacco Smoke in Air

OSHA has published a proposed rule for IAQ (including tobacco smoke in the workplace), and this rulemaking is likely to be completed in the near future. Smoking
policies should include provisions for dedicated smoking areas. Dedicated smoking areas should be configured so that migration of smoke into nonsmoking areas
will not occur. Such areas should:

have floor-to-ceiling walls of tight construction;
be under negative pressure relative to adjacent areas; AND
be exhausted outside the building and not recirculated.

For more information on investigation of complaints, CSHO’s should consult the NIOSH Guidance for Indoor Air Quality Investigation and the EPA guide Building Air
Quality (1991).

VI. Bibliography

American Conference of Governmental Industrial Hygienists (ACGIH). 1988. Industrial Ventilation, a Manual of Recommended Practice. 20th ed. Cincinnati, OH:
American Conference of Governmental Industrial Hygienists.

Air Movement and Control Association (AMCA). 1988. AMCA Publication One. Arlington Heights, IL: Air Movement and Control Association.

American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Handbooks and Standards. Atlanta, GA: American Society of Heating,
Refrigerating, and Air-Conditioning Engineers.

Sheet Metal and Air Conditioning Contractors National Association (SMACNA). SMACNA Publications. Arlington, VA: Sheet Metal and Air Conditioning Contractors
National Association.

American National Standards Institute (ANSI) Standards:

Z9.1 – Open Surface Tanks Operation
Z9.2 – Fundamentals Covering the Design and Operation of Local Exhaust Systems
Z9.3 – Design, Construction, and Ventilation of Spray Finishing Operations
Z9.4 – Ventilation and Safe Practice of Abrasive Blasting Operations
Z9.5 – Laboratory Ventilation. Fairfax, VA: American Industrial Hygiene Association.

Burgess, W. A. et al. 1989. Ventilation and Control of the Work Environment. New York: Wiley Interscience.

Burton, D. J. 1989. Industrial Ventilation Workbook. Salt Lake City, UT: IVE, Inc.

Burton, D. J. 1990. Indoor Air Quality Workbook. Salt Lake City, UT: IVE, Inc.

Jorgensen, R. et al. 1983. Fan Engineering. 8th ed. Buffalo, NY: Buffalo Forge Co.

Homeon, W. C. L. 1963. Plant and Process Ventilation. New York: Industrial Press.

National Institute for Occupational Safety and Health (NIOSH). 1987. Guidance for Indoor Air Quality Investigations. Cincinnati: NIOSH.

OSHA Field Operations Manual. 1992. OSHA Instruction CPL 2.45B. Washington, D.C.: U.S. Government Printing Office.

U.S. Environmental Protection Agency (EPA). 1991. Building Air Quality.

Appendix III:3-1. Ventilation Primer

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Table III:3-5. Selection Criteria for General and Local Exhaust Systems

General exhaust ventilation (dilution ventilation) is appropriate when:
Emission sources contain materials of relatively low hazard. (The degree of hazard is related to
toxicity, dose rate, and individual susceptibility);
Emission sources are primarily vapors or gases, or small, respirable-size aerosols (those not likely to
settle);
Emissions occur uniformly;
Emissions are widely dispersed;
Moderate climatic conditions prevail;
Heat is to be removed from the space by flushing it with outside air;
Concentrations of vapors are to be reduced in an enclosure; and
Portable or mobile emission sources are to be controlled.

Local exhaust ventilating is appropriate when:
Emission sources contain materials of relatively high hazard;
Emitted materials are primarily larger-diameter particulates (likely to settle);
Emissions vary over time;
Emission sources consist of point sources;
Employees work in the immediate vicinity of the emission source;
The plant is located in a severe climate; and
Minimizing air turnover is necessary.

where: q = evaporation rate in acfm
387 = volume in cubic feet formed by the evaporation of one lb-mole of a substance, e.g., a solvent
MW = molecular weight of emitted material
lbs = lbs of material evaporated
min = time of evaporation
d = density correction factor

where: Q = volume flow rate of air, in acfm
q = evaporation rate, in acfm
K = mixing factor to account for poor or random mixing (NOTE: K = 2 to 5; K = 2 is optimum)
C = acceptable airborne concentration of the material (typically half of the PEL).

Selection

Before an appropriate ventilation system can be selected, the employer should study emission sources, worker behavior, and air movement in the area. In some
cases the employer may wish to seek the services of an experienced professional ventilation engineer to assist in the data gathering. Table III:3-5 shows factors to
consider when selecting a ventilation system. Combinations of controls are often employed for HVAC purposes.

General Exhaust (Dilution) Ventilation Systems

General exhaust ventilation, also called dilution ventilation, is different from local exhaust ventilation because instead of capturing emissions at their source and
removing them from the air, general exhaust ventilation allows the contaminant to be emitted into the workplace air and then dilutes the concentration of the
contaminant to an acceptable level (e.g., to the PEL or below). Dilution systems are often used to control evaporated liquids.

To determine the correct volume flow rate for dilution (Q ), it is necessary to estimate the evaporation rate of the contaminant (q ) according to the following
equation:

q = [(387)(lbs)]/[(MW)(min)(d)]

The appropriate dilution volume flow rate for toxics is:

Q = [(q )(K )(10 )]/C

The number of air changes per hour is the number of times one volume of air is replaced in the space per hour. In practice, replacement depends on mixing
efficiency. When using dilution ventilation:

position exhausts as close to emission sources as possible;
use auxiliary fans for mixing;

d d

d
d

d d m
6

a
d
d

m m m

a

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where: K = loss factor
VP = velocity pressure in duct
|SP | = absolute static pressure about 5 duct diameters down the duct from the hood.

C = Q =√VP =√1

Q SP 1 + K

where: K = loss factor
VP = velocity pressure in duct
SP = absolute static pressure about 5 duct diameters down the duct from the hood.

make sure employees are upwind of the dilution zone; and
add make-up air where it will be most effective.

Local Exhaust Ventilation Systems

A typical local exhaust ventilation system is composed of five parts: fans, hoods, ducts, air cleaners, and stacks. Local exhaust ventilation is designed to capture an
emitted contaminant at or near its source, before the contaminant has a chance to disperse into the workplace air.

Fan Selection. To choose the proper fan for a ventilation system, this information must be known:

air volume to be moved;
fan static pressure;
type and concentration of contaminants in the air (because this affects the fan type and materials of construction); and
the importance of noise as a limiting factor.

Once this information is available, the type of fan best suited for the system can be chosen. Many different fans are available, although they all fall into one of two
classes: axial flow fans and centrifugal fans. For a detailed explanation of fans, see the ACGIH Industrial Ventilation Manual.

Hoods. The hood captures, contains, or receives contaminants generated at an emission source. The hood converts duct static pressure to velocity pressure and
hood entry losses (e.g., slot and duct entry losses).

Hood entry loss (H ) is calculated according to the following equation:

H = (K)(VP) = |SP | = VP

A hood’s ability to convert static pressure to velocity pressure is given by the coefficient of entry (C ), as follows:

To minimize air-flow requirements, the operation should be enclosed as much as possible, either with a ventilated enclosure, side baffles, or curtains. This helps
both to contain the material and to minimize the effect of room air.

When using a capture or receiving hood, the hood should be located as close to the contaminant source as possible. Reducing the amount of contaminants
generated or released from the process reduces ventilation requirements.

The hood should be designed to achieve good air distribution into the hood openings so that all the air drawn into the hood helps to control contaminants. Avoid
designs that require that the velocities through some openings be very high in order to develop the minimum acceptable velocity through other openings or parts
of the hood.

The purpose of most ventilation systems is to prevent worker inhalation of contaminants. For this reason, the hood should be located so that contaminants are not
drawn through the worker’s breathing zone. This is especially important where workers lean over an operation such as an open-surface tank or welding bench.

Hoods must meet the design criteria in the ACGIH Industrial Ventilation Manual or applicable OSHA standards. Most hood design recommendations account for
cross-drafts that interfere with hood operation. Strong cross-drafts can easily reduce a hood’s effectiveness by 75%. Standard hood designs may not be adequate
to contain highly toxic materials.

The hood should be designed to cause minimum interference with the performance of work. Positioning access doors inside an enclosure that must be opened and
closed often means that in practice the doors will be left open, and locating capture hoods too close to the process for the worker’s convenience often means that
the hood will be disassembled and removed. Hoods should never increase the likelihood of mechanical injury by interfering with a worker’s freedom to move
around machinery.

Two common misconceptions about hoods that are a part of local exhaust systems are:

Hoods draw air from a significant distance away from the hood opening, and therefore they can control contaminants released some distance away. It is easy
to confuse a fan’s ability to blow a jet of air with its ability to draw air into a hood. Hoods must be close to the source of contamination to be effective.

e

e h

h
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e ideal

actual h

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Heavier-than-air vapors tend to settle to the workroom floor and therefore can be collected by a hood located there. A small amount of contaminant in the air
(1,000 ppm means 1,000 parts of contaminant plus 999,000 parts of air) has a resulting density close to that of air, and random air currents will disperse the
material throughout the room.

Ducts. Air flows turbulently through ducts at between 2,000-6,000 feet per minute (fpm). Ducts can be made of galvanized metal, fiberglass, plastic, and
concrete. Friction losses vary according to ductwork type, length of duct, velocity of air, duct area, density of air, and duct diameter.

Air Cleaners. The design of the air cleaner depends on the degree of cleaning required. Regular maintenance of air cleaners increases their efficiency and
minimizes worker exposure. Different types of air cleaners are made to remove particulates (e.g., precipitators, cyclones, etc.) and gases and vapors (e.g.,
scrubbers).

Stacks. Stacks disperse exhaust air into the ambient environment. The amount of reentrainment depends on exhaust volume, wind speed and direction,
temperature, location of intakes and exhausts, etc. When installing stacks:

Provide ample stack height (a minimum of 10 ft above adjacent rooflines or air intakes);
Place stack downwind of air intakes;
Provide a stack velocity of a minimum of 1.4 times the wind velocity;
Place the stack as far from the intake as possible (50 ft is recommended);
Place the stack at least 10 ft high on most roofs to avoid recirculation; and
Avoid rain caps if the air intake is within 50 ft of the stack.

Make-up Air Systems

Exhaust ventilation systems require the replacement of exhausted air. Replacement air is often called make-up air. Replacement air can be supplied naturally by
atmospheric pressure through open doors, windows, wall louvers, and adjacent spaces (acceptable), as well as through cracks in walls and windows, beneath
doors, and through roof vents (unacceptable). Make-up air can also be provided through dedicated replacement air systems. Generally, exhaust systems are
interlocked with a dedicated make-up air system.

Other reasons for designing and providing dedicated make-up air systems are that they:

Avoid high-velocity drafts through cracks in walls, under doors, and through windows;
Avoid differential pressures on doors, exits, and windows; and
Provide an opportunity to temper the replacement air.

If make-up air is not provided, a slight negative pressure will be created in the room and air flow through the exhaust system will be reduced.

HVAC

HVAC (heating, ventilating, and air-conditioning) is a common term that can also include cooling, humidifying or dehumidifying, or otherwise conditioning air for
comfort and health. HVAC also is used for odor control and the maintenance of acceptable concentrations of carbon dioxide.

Air-conditioning has come to include any process that modifies the air for a work or living space: heating or cooling, humidity control, and air cleaning. Historically,
air-conditioning has been used in industry to improve or protect machinery, products, and processes. The conditioning of air for humans has become normal and
expected. Although the initial costs of air conditioning are high, annual costs may account only for about 1% to 5% of total annual operating expenses. Improved
human productivity, lower absenteeism, better health, and reduced housekeeping and maintenance almost always make air-conditioning cost effective.

Mechanical air-handling systems can range from simple to complex. All distribute air in a manner designed to meet ventilation, temperature, humidity, and air-
quality requirements established by the user. Individual units may be installed in the space they serve, or central units can serve multiple areas.

HVAC engineers refer to the areas served by an air handling system as zones. The smaller the zone, the greater the likelihood that good control will be achieved;
however, equipment and maintenance costs are directly related to the number of zones. Some systems are designed to provide individual control of rooms in a
multiple-zone system.

Both the provision and distribution of make-up air are important to the proper functioning of the system. The correct amount of air should be supplied to the
space. Supply registers should be positioned to avoid disruption of emission and exposure controls and to aid dilution efforts.

Considerations in designing an air-handling system include volume flow rate, temperature, humidity, and air quality. Equipment selected must be properly sized and
may include:

outdoor air plenums or ducts
filters
supply fans and supply air systems
heating and cooling coils
humidity control equipment
supply ducts
distribution ducts, boxes, plenums, and registers
dampers
return air plenums

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Table III:3-6. Recirculation Criteria

Protection of employees must be the primary design consideration.
The system should remove as much of the contaminant as can economically be separated from
exhaust air.
The system should not be designed simply to achieve PEL levels of exposure.
The system should never allow recirculation to significantly increase existing exposures.
Recirculation should not be used if a carcinogen is present.
The system should have fail-safe features, e.g., warning devices on critical parts, back-up systems.
Cleaning and filtering devices that ensure continuous and reliable collection of the contaminant
should be used.
The system should provide a by-pass or auxiliary exhaust system for use during system failure.
The system should include feedback devices that monitor system performance, e.g., static pressure
taps, particulate counters, amperage monitors.
The system should be designed not to recirculate air during equipment malfunction.
The employer should train employees in the use and operation of the system.

acfm
Actual cubic feet per minute of gas flowing at existing temperature and
pressure. (See also scfm.)

ACH, AC/H (air changes per hour)
The number of times air is replaced in an hour.

Air Density
The weight of air in lbs per cubic foot. Dry standard air at T=68° F (20° C)
and BP = 29.92 in Hg (760 mm Hg) has a density of 0.075 lb/cu ft.

Anemometer
A device that measures the velocity of air. Common types include the
swinging vane and the hot-wire anemometer.

Area (A)
The cross-sectional area through which air moves. Area may refer to the
cross-sectional area of a duct, a window, a door, or any space through which
air moves.

Atmospheric Pressure
The pressure exerted in all directions by the atmosphere. At sea level, mean
atmospheric pressure is 29.92 in Hg, 14.7 psi, 407 in w.g., or 760 mm Hg.

Brake Horsepower (bhp)
The actual horsepower required to move air through a ventilation system
against a fixed total pressure plus the losses in the fan. bhp=ahp x 1/eff,
where eff is fan mechanical efficiency.

Branch
In a junction of two ducts, the branch is the duct with the lowest volume flow
rate. The branch usually enters the main at an angle of less than 90.

Canopy Hood (Receiving Hood)
A one- or two-sided overhead hood that receives rising hot air or gas.

Capture Velocity

in. w.g. (inches of water)
A unit of pressure. One inch of water is equal to 0.0735 in. of mercury, or
0.036 psi. Atmospheric pressure at standard conditions is 407 in. w.g.

Industrial Ventilation (IV)
The equipment or operation associated with the supply or exhaust of air by
natural or mechanical means to control occupational hazards in the industrial
setting.

Laminar Flow (also Streamline Flow)
Air flow in which air molecules travel parallel to all other molecules; laminar
flow is characterized by the absence of turbulence.

Local Exhaust

Ventilation

An industrial ventilation system that captures and removes emitted
contaminants before dilution into the ambient air of the workplace.

Loss
Usually refers to the conversion of static pressure to heat in components of
the ventilation system, e.g., “the hood entry loss.”

Make-Up Air
See Replacement and Compensating Air.

Manometer
A device that measures pressure difference; usually a U-shaped glass tube
containing water or mercury.

Minimum Transport Velocity (MTV)
The minimum velocity that will transport particles in a duct with little settling;
MTV varies with air density, particulate loading, and other factors.

Outdoor Air (OA)
Outdoor air is the “fresh” air mixed with return air (RA) to dilute contaminants
in the supply air.

Pitot Tube

exhaust air provisions
return fans
controls and instrumentation

Recirculation

Although not generally recommended, recirculation is an alternative to air exchanging. Where used, recirculation should incorporate air cleaners, a by-pass or
auxiliary exhaust system, regular maintenance and inspection, and devices to monitor system performance. Key points to consider in the use of recirculation are
shown in Table III:3-6.

Appendix III:3-2. Glossary

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The velocity of air induced by a hood to capture emitted contaminants
external to the hood.

Coefficient of Entry (C )
A measure of the efficiency of a hood’s ability to convert static pressure to
velocity pressure; the ratio of actual flow to ideal flow.

Density Correction Factor
A factor applied to correct or convert dry air density of any temperature to
velocity pressure; the ratio of actual flow to ideal flow.

Dilution Ventilation (General Exhaust Ventilation)
A form of exposure control that involves providing enough air in the
workplace to dilute the concentration of airborne contaminants to acceptable
levels.

Entry Loss
See Hood Entry Loss or Branch Entry Loss.

Evase (pronounced eh-va-say)
A cone-shaped exhaust stack that recaptures static pressure from velocity
pressure.

Fan
A mechanical device that moves air and creates static pressure.

Fan Laws
Relationships that describe theoretical, mutual performance changes in
pressure, flow rate, rpm of the fan, horsepower, density of air, fan size, and
sound power.

Fan Curve
A curve relating pressure and volume flow rate of a given fan at a fixed fan
speed (rpm).

Friction Loss
The static pressure loss in a system caused by friction between moving air
and the duct wall, expressed as in w.g./100 ft, or fractions of VP per 100 ft of
duct (mm w.g./m; Kpa/m).

Gauge Pressure
The difference between two absolute pressures, one of which is usually
atmospheric pressure.

General Exhaust
See Dilution Ventilation.

Head
Pressure, e.g. “The head is 1 in w.g.”

Hood
A device that encloses, captures, or receives emitted contaminants.

Hood Entry Loss (H )
The static pressure lost (in inches of water) when air enters a duct through a
hood. The majority of the loss usually is associated with a vena contracta
formed in the duct.

Hood Static Pressure (SP )
The sum of the duct velocity pressure and the hood entry loss; hood static
pressure is the static pressure required to accelerate air at rest outside the
hood into the duct at velocity.

HVAC (Heating, Ventilation, and Air Conditioning) Systems
Ventilating systems designed primarily to control temperature, humidity,
odors, and air quality.

Indoor Air Quality (IAQ), Sick-Building Syndrome, Tight-Building
Syndrome

The study, examination, and control of air quality related to temperature,
humidity, and airborne contaminants.

A device used to measure total and static pressures in an airstream.
Plenum

A low-velocity chamber used to distribute static pressure throughout its
interior.

Pressure Drop
The loss of static pressure across a point; for example, “the pressure drop
across an orifice is 2.0 in. w.g.”

Replacement Air (also, Compensating Air, Make-Up Air)
Air supplied to a space to replace exhausted air.

Return Air
Air that is returned from the primary space to the fan for recirculation.

scfm
Standard cubic feet per minute. A measure of air flow at standard conditions,
i.e., dry air at 29.92 in. Hg (760 mm Hg) (gauge), 68° F (20° C).

Slot Velocity
The average velocity of air through a slot. Slot velocity is calculated by
dividing the total volume flow rate by the slot area (usually, Vs = 2,000 fpm).

Stack
A device on the end of a ventilation system that disperses exhaust
contaminants for dilution by the atmosphere.

Standard Air, Standard Conditions
Dry air at 68° F (20° C), 29.92 in Hg (760 mm Hg).

Static Pressure (SP)
The pressure developed in a duct by a fan; the force in inches of water
measured perpendicular to flow at the wall of the duct; the difference in
pressure between atmospheric pressure and the absolute pressure inside a
duct, cleaner, or other equipment; SP exerts influence in all directions.

Suction Pressure
(See Static Pressure.) An archaic term that refers to static pressure on the
upstream side of the fan.

Total Pressure
The pressure exerted in a duct, i.e., the sum of the static pressure and the
velocity pressure; also called Impact Pressure, Dynamic Pressure.

Transport Velocity
See Minimum Transport Velocity.

Turbulent Flow
Air flow characterized by transverse velocity components as well as velocity in
the primary direction of flow in a duct; mixing velocities.

Velocity (V)
The time rate of movement of air; usually expressed as feet per minute.

Velocity Pressure (VP)
The pressure attributed to the velocity of air.

Volume Flow Rate (Q)
Quantity of air flow in cfm, scfm, or acfm.

Appendix III:3-3. OSHA and Consensus Standards
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29 CFR 1910.94(a) Abrasive blasting

29 CFR 1910.94(b) Grinding, polishing, and buffing operations

29 CFR 1910.94(d) Open surface tanks

29 CFR 1910.252(c)(2)(i)(a) and (b); (c)(2)(ii) Ventilation for general welding and cutting–General

29 CFR 1910.252(c)(3) Local exhaust hoods and booths

29 CFR 1910.252(c)(5)(ii) Fluorine compounds–Maximum allowable concentration

29 CFR 1910.252(c)(12) Cutting of stainless steels

29 CFR 1910.1003 to .1016 Carcinogens

29 CFR 1910.1025(e)(5) Lead

29 CFR 1910.1027(f)(3) Cadmium

29 CFR 1926.27(a) Ventilation–General

29 CFR 1926.62(e)(3) Lead

29 CFR 1926.63(f)(4) Cadmium

29 CFR 1926.154(a)(1) Temporary heating devices–Ventilation

29 CFR 1926.353(e)(1) Ventilation and protection in welding, cutting and h eating–
Gal welding, cutting, and heating

29 CFR 1915.32(a)(2) Toxic cleaning solvents

29 CFR 1915.51(f)(1) Ventilation and protection in welding, cutting, and heating–
General welding, cutting, and heating

29 CFR 1918.93(a)(1)(iii) Ventilation and atmospheric conditions

29 CFR 1910.94(a)(3)(i)(d) Abrasive blasting–Blasting cleaning

29 CFR 1910.94(a)(5) Abrasive blasting–Personal protective equipment

29 CFR 1910.94(a)(6) Abrasive blasting–Air supply and air compressors

29 CFR 1910.94(a)(7) Abrasive blasting–Operational procedures and general safety

I. OSHA Standards
A. Health-Related Ventilation Standards. This list includes some, but not necessarily all, OSHA standards that address the control of employee exposure

to recognized contaminants.)

General Industry

Construction

Maritime

B. Health-Related Ventilation Standards Other Than Airflow. This list includes some, but not necessarily all, OSHA standards that do not contain
airflow requirements but are located in the health-related ventilation standards.

General Industry

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29 CFR 1910.94(d)(9) Open surface tanks–Personal protection

29 CFR 1910.94(d)(10) Open surface tanks–Special precautions for cyanide

29 CFR 1910.94(d)(11) Open surface tanks–Inspection, installation and maintenance

29 CFR 1910.94(d)(12) Open surface tanks–Vapor degreasing tanks

29 CFR 1910.94(c) Ventilation–Spray finishing operations

29 CFR 1910.103(b)(3)(ii)(b) Hydrogen–Gaseous hydrogen systems–Separate buildings

29 CFR 1910.103(b)(3)(iii)(b) Hydrogen–Gaseous hydrogen systems–Special rooms

29 CFR 1910.103(c)(3)(ii)(b) Hydrogen–Liquid hydrogen systems–Separate buildings

29 CFR 1910.103(c)(3)(iii)(b) Hydrogen–Liquid hydrogen systems–Special rooms

29 CFR 1910.104(b)(3)(xii) Oxygen–Bulk oxygen systems–Ventilation

29 CFR 1910.104(b)(8)(vii) Oxygen–Bulk oxygen systems–

Venting

29 CFR 1910.106(d)(4)(iv) Flammable and combustible liquids–Container and portable
tank storage–Design and construction of inside storage room-
-Ventilation

29 CFR 1910.106(e)(3)(v) Flammable and combustible liquids–Industrial plants–Unit
physical operations–Ventilation

29 CFR 1910.106(f)(2)(iii)(a) Flammable and combustible liquids–Bulk plants–Building–
Ventilation

29 CFR 1910.106(h)(3)(iii) Flammable and combustible liquids–Processing plants–
Processing building–Ventilation

29 CFR 1910.107(b)(5)(i) Spray finishing using flammable and combustible materials–
Spray booths–Dry type overspray collectors

29 CFR 1910.107(d)(1) and (2) Spray finishing using flammable and combustible materials–
Ventilation–Conformance–General

29 CFR 1910.107(i)(9) Spray finishing using flammable and combustible materials–
Electrostatic hand spraying equipment–Ventilation

29 CFR 1910.108(b)(1) and (2) Dip tanks containing flammable combustible liquids–
Ventilation–Ventilation combined with drying

29 CFR 1910.307 Hazardous (classified) locations

29 CFR 1915.12(a)(2) Precautions before entering–Flammable atmospheres and
residues

29 CFR 1915.13(a)(2) Cleaning and other cold work (flammable vapors)

C. Fire and Explosion-Related Ventilation Standards. This list includes some, but not necessarily all, OSHA standards that are intended to prevent fire
and explosions.

General Industry

D. Exceptions to 25% of the LEL for Fire and Explosion-Related Standards. This list includes but is not limited to OSHA standards that allow
concentrations of flammable materials no greater than 10% of the LEL.

Maritime

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29 CFR 1915.35(b)(1), (2), (3) Painting–Paints and tanks coatings dissolved in highly volatile,
toxic and/or flammable solvents

29 CFR 1915.36(a)(2) Flammable liquids ventilation

29 CFR 1926.803(i)(2) Compressed Air–Ventilation and air quality–(Tunnels)

29 CFR 1910.252(c)(2)(i)(c) Welding, cutting and brazing–Health protection and
ventilating–Ventilation for general welding and cutting–
General

29 CFR 1910.252(c)(4) Welding, cutting and brazing–Health protection and
ventilating–Ventilation in confined spaces

29 CFR 1910.252(c)(5)(i) Welding, cutting and brazing–Fluorine compounds

29 CFR 1910.252(c)(6)(i) Welding, cutting and brazing–Zinc–Confined spaces

29 CFR 1910.252(c)(7)(i) Welding, cutting and brazing–Lead–Confined spaces

29 CFR 1910.252(c)(8) Welding, cutting and brazing–Beryllium

29 CFR 1910.252(c)(9) Welding, cutting and brazing–Cadmium

29 CFR 1910.252(c)(10) Welding, cutting and brazing–Mercury

29 CFR 1926.154(a)(2) Temporary heating devices–Ventilation

29 CFR 1926.353(b)(1) Ventilation and protection in welding, cutting and heating–
Welding, cutting and heating in confined spaces

29 CFR 1926.353(c)(1) and (2) Ventilation and protection in welding, cutting and heating–
Welding, cutting or heating of metals of toxic significance

29 CFR 1926.800(k) Tunnels and shafts–Air quality and ventilation

29 CFR 1915.12(b)(2) Precautions before entering–Toxic atmospheres and residues

29 CFR 1915.12(c)(2) Precautions before entering–Oxygen deficient atmospheres

29 CFR 1915.12(d) Precautions before entering–Exceptions

29 CFR 1915.34(a)(4) Mechanical paint removers–Power tools–(paint dust)

29 CFR 1915.51(c)(3) Ventilation and protection in welding, cutting and heating–
Welding, cutting and heating confined spaces

29 CFR 1915.51(d)(1) and (2) Ventilation and protection in welding, cutting and heating–
cutting or heating of metals of toxic significance.

Standard Source Title

Construction

E. Special Conditions Standards. This list includes some but not necessarily all OSHA standards that involve confined space operations and/or high-
hazard contaminants specifically designated in the standard.

General Industry
Construction
Maritime

II. Consensus Standards

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Air filters

ASHRAE 52-76 ASHRAE Methods of Testing Air-Cleaning Devices Used in General Ventilation for
Removing Particulate Matter

Exhaust systems

ANSI Z33.1-
1982
NFPA 91-1983

NFPA Installation of Blower and Exhaust Systems for Dust, Stock, Vapor
Removal or Conveying (1983)

ANSI Z9.2-
1979

AIHA Fundamentals Governing the Design and Operation of Local Exhaust
Systems

ANSI Z9.1-
1977

AIHA
ASHRAE

Practices for Ventilation and Operation of Open-Surface Tanks

ANSI Z9.3-
1964

ANSI Safety Code for Design, Construction, and Ventilation of Spray Finishing
Operations (reaffirmed 1971)

ANSI Z9.4-
1979
ANSI Z9.4A-
1981

ANSI Ventilation and Safe Practices of Abrasives Blasting Operations

ANSI Z9.5-
1992

AIHA Laboratory Ventilation

Fans

AMCA 99-83
ANSI/UL 507-
1976

AMCA
UL

Standards Handbook Electric Fans (1977)

ASHRAE 51-75
AMCA 210-74

ASHRAE Laboratory Methods of Testing Fans for Rating

ANSI/ASHRAE
87.7-1983

ASHRAE Methods of Testing Dynamic Characteristics of Propeller Fans–
Aerodynamically Excited Fan Vibrations and Critical Speeds

AMCA 210-74 AMCA Laboratory Methods of Testing Fans for Rating Purposes

AMCA 99-
2404-78

AMCA Drive Arrangement for Centrifugal Fans

AMCA 99-
2406-83

AMCA Designation for Rotation and Discharge of Centrifugal Fans

AMCA 99-
2407-66

AMCA Motor Positions for Belt or Chain Drive Centrifugal Fans

AMCA 99-
2410-82

AMCA Drive Arrangement for Tubular Centrifugal Fans

Industrial Duct

SMACNA SMACNA Round Industrial Duct Construction

SMACNA SMACNA Rectangular Industrial Duct Construction

Venting

NFPA 68 NFPA Guide for Explosion Venting

NFPA 204M NFPA Guide for Smoke and Heat Venting

SMACNA SMACNA Guide for Steel Stack Design and Construction (1983)

Ventilation

NFPA 96 NFPA Vapor Removal from Cooking Equipment (1984)

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NFPA-88A, 88B NFPA Parking Structures (1979); Repair Garages (1979)

ASHRAE 62-
1989

ASHARAE Ventilation for Acceptable Indoor Air Quality

ACGIH ACGIH Industrial Ventilation

Source Organization

ACGIH American Conference of Governmental Industrial Hygienists
6500 Glenway Ave., Bldg. D-5
Cincinnati, OH 45211

AIHA American Industrial Hygiene Association
2700 Prosperity Ave., Suite 250
Fairfax, VA 22031-4319

AMCA Air Movement and Control Association
30 W. University Dr.
Arlington Heights, IL 60004

ANSI American National Standards Institute
1430 Broadway
New York, NY 10018

ASHRAE American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc.
1791 Tullie Circle, N.E.,
Atlanta, GA 30329

NFPA National Fire Protection Association
Batterymarch Park
Quincy, MA 02269

SMACNA Sheet Metal and Air Conditioning Contractors’ National Association
8224 Old Courthouse Rd.
Vienna, VA 22180

UL Underwriters Laboratories Inc.
333 Pfingsten Rd.
Northbrook, IL 60062

III. Sources of Consensus Standards

Copies of the consensus standards are published and available directly from the organization issuing the standard. A minimal fee is often required.

Appendix III:3-4. Troubleshooting an Exhaust System–Some Helpful Hints

Most of the following checks can be made by visual observation and do not require extensive measurements.

If air flow is low in hoods, check:

Fan rotation (reversed polarity will cause fan to run backwards; a backward-running centrifugal fan delivers only 30-50% of rated flow);
Fan RPM;
Slipping belt;
Clogged or corroded fan wheel and casing;
Clogged ductwork (high hood static pressure and low air flow may indicate restricted ducts; open clean-out doors and inspect inside ducts);
Closed dampers in ductwork;
Clogged collector or air cleaning devices;
Weather cap too close to discharge stack (a ¾ duct- diameter gap should exist between cap and stack; weather caps are not recommended);
Poorly designed ductwork (short radius elbows); (branch entries enter main duct at sharp angles); (ductwork diameter too small for the air-flow needed; and
Lack of make-up air (high negative pressures affect propeller fan system output; lack of supplied make-up air causes high airflow velocities at doors and
windows).

If air flow is satisfactory in a hood but contaminant control is poor, check:

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1

Course Learning Outcomes for Unit VII

Upon completion of this unit, students should be able to:

7. Evaluate types of hazard controls.
7.1 Discuss the use of elimination/substitution for controlling occupational hazards.
7.2 Discuss the use of engineering controls for occupational hazards.
7.3 Discuss the use of administrative controls for occupational hazards.

Reading Assignment

To access the following resources, click on the links below:

Occupational Safety and Health Administration. (n.d.). Chemical hazards and toxic substances: Controlling
exposures. Retrieved from https://www.osha.gov/SLTC/hazardoustoxicsubstances/control.html

Occupational Safety and Health Administration. (n.d.). Basic hazard awareness [PowerPoint slides].
Retrieved from https://www.osha.gov/sites/default/files/2018-11/fy10_sh-20839-
10_basic_hazard_awareness.pptx

Occupational Safety and Health Administration. (n.d.). OSHA technical manual—Section III: Chapter

3

Ventilation Investigation. Retrieved from https://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_3.html

Unit Lesson

The last of the four tenets of industrial hygiene that we will study is control. The first three tenets—
anticipation, recognition, and evaluation—identify hazards and the level of risk for each hazard. Controls then
are used to reduce the risk associated with the hazards to an acceptable level. Risk assessment is a valuable
tool in prioritizing expenditures for control methods. Controls will be implemented first for hazards with the

highest level of risk.

The Occupational Safety and Health Administration (OSHA) established a hierarchy of controls for
occupational hazards. It illustrates OSHA’s preferred approach for hazard control. As summarized in the
diagram below, the Hierarchy of Controls includes elimination/substitution, engineering controls,
administrative controls (including work practices), and personal protective equipment (PPE).

In looking at protection from occupational hazards, the most effective method is to prevent an exposure from
occurring in the first place; however, this is not always possible in occupational settings. Therefore, the next

Course/Unit
Learning Outcomes

Learning Activity

7.1
Unit VII Lesson
Article: “Basic hazard awareness [PowerPoint slides]”
Unit VII Assessment

7.2
Unit VII Lesson
Unit VII Assessment

7.3
Unit VII Lesson
Article: “Basic hazard awareness [PowerPoint slides]”
Unit VII Assessment

UNIT VII STUDY GUIDE

Hazard Controls

https://www.osha.gov/SLTC/hazardoustoxicsubstances/control.html

https://www.osha.gov/sites/default/files/2018-11/fy10_sh-20839-10_basic_hazard_awareness.pptx

https://www.osha.gov/sites/default/files/2018-11/fy10_sh-20839-10_basic_hazard_awareness.pptx

https://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_3.html

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UNIT x STUDY GUIDE

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priority is to prevent harm to exposed individuals. Finally, if harm occurs, the priority is to limit the harm as
much as possible. OSHA’s Hierarchy of Controls is designed to meet these priorities.

The first control method in OSHA’s
Hierarchy of Controls is
elimination/substitution. This control method
is always the most effective and preferred
method because it prevents the exposure
from occurring in the first place. If you
remove a specific hazard completely from a
workplace, no one can be exposed to that
hazard. For example, if a facility is using a
solution containing styrene to clean parts,
there is a health risk from exposure to the
styrene, both through inhalation and dermal
exposure.

If the facility determined that the cleaning
could be performed using only water, the
exposure to styrene would be completely
eliminated for that particular task. This
approach sounds simple but is much more
complicated in practice. If, for example, a
solvent solution is needed to clean a part,
water would not be effective. Therefore, this
approach would change to evaluating other
chemicals effective in performing the same
task and choosing one that would produce

the lowest risk to employees. In the example above, some employers have changed from a solvent like
styrene to a solvent like acetone. Acetone has a lower toxicity than styrene, so health risks will be reduced.
Nevertheless, reducing a health risk may increase other risks. Acetone is more flammable than styrene, so
substituting acetone may reduce health risks but increase the risk of a fire. Of course, there may be situations
where specifications require the use of a specific chemical and thus the use of elimination/substitution is
untenable.

If the hazard cannot be eliminated from the workplace, residual risks will remain. Additional controls will be
designed to reduce the risk associated with the hazard. In evaluating the use of control methods, one must
always ask what level of residual risk will be acceptable. Once the acceptable level of residual risk has been
determined, the rest of the controls in OSHA’s Hierarchy of Controls can be applied, in order of preference,
until the residual risk has been lowered to the acceptable level.

The acceptable level of residual risk is a debated topic. Certainly, for exposures to chemical and physical
hazards that industrial hygienists evaluate, the established OSHA permissible exposure limits (PELs)
represent what should be accepted as residual risks. One would think exposures below the OSHA PELs are
either safe or at least below a level where the residual risk would be significant, but this is not always true.
OSHA should consider technological and economic feasibility in addition to risk assessments when they
establish PELs. In some instances, exposures at the established PELs continue to carry significant risks of
morbidity and mortality, even by OSHA’s definition of significant risk.

OSHA has historically used a residual risk of 1 in 1,000 as being significant; this is based on a Supreme Court
decision in 1980. Any residual risk exceeding that level is considered significant by OSHA. In many cases,
OSHA has estimated the residual risk to exceed this level for lifetime exposures at new PELs. For example,
OSHA recently released new PELs for crystalline silica. Under the old PELs, OSHA estimated the risk of
death from silicosis to be 11:1,000 in general industry and 17:1,000 in the construction industry. For
exposures at the newly published PEL, OSHA estimates the risk of death from silicosis at 7:1,000 for both
general industry and construction. At the new action level, OSHA estimates the risk of death from silicosis at
4:1,000 for both general industry and construction. Significant residual risk of death is also present for
exposures at the PEL for both asbestos and hexavalent chromium. For this reason, many employers may
choose to use more stringent control methods than those required by OSHA.

Basic hazard awareness diagram
(Occupational Safety and Health Administration [OSHA], n.d.)

3
UNIT x STUDY GUIDE

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The next preferred control method in the Hierarchy of Controls is engineering controls. Because it may be
difficult to eliminate a hazard or substitute a less hazardous chemical for a process, engineering controls are
the most commonly used control method for occupational settings. Many different engineering controls are
used. In some cases, the process can be isolated or enclosed to separate the worker from the hazard. An
example would be to place a machining process inside an enclosure with a lid that opens and closes and to
provide automatic sprayers that apply metalworking fluids. The employee opens the door to the machine,
removes the part, and places another part inside the machine. The metalworking fluid is not applied, and the
machining process will not start until the door is closed. Industrial hygiene evaluations have shown that
exposures to metalworking fluids still occur because the hazard is still present, but the exposures are lower
than they would be with an open process.

Engineering controls can also address noise hazards, for example, in using enclosure and isolation methods
to reduce noise hazard risk. The enclosures, however, will require the use of specific materials. As discussed
in Unit VI, noise propagates through air as a wave, and noise hazards from a single source can be present at
different frequencies. Noise-deadening materials are typically effective at reducing dB levels based on
frequencies. The use of the octave band filter with a sound level meter, as discussed in Unit VI, can provide
the information necessary to choose materials for a noise enclosure that will be effective in reducing noise
levels from a specific source.

Another engineering control involves wet methods. These methods are specified in some regulations such as
OSHA’s asbestos in construction regulation. Because significant residual risk remains for exposures at the
PEL, OSHA has specified wet methods (and respiratory protection) for some tasks involving asbestos
removal, even if exposures have been shown to be below the PEL. Wet methods are designed to reduce, but
not completely eliminate, the concentration of an aerosol hazard in the air.

Ventilation is one of the most common engineering controls. Two types of ventilation can reduce exposure to
hazards: general dilution ventilation and local exhaust ventilation (LEV) systems. The nature of a hazard and
the risk associated with that hazard, will help determine the ventilation system with the best protection.

General dilution ventilation systems merely blow fresh air into a work area to dilute the concentration of an air
hazard. A typical dilution ventilation system in a workplace consists of a fan or fans in the ceiling or through
an exterior wall. The fans blow either fresh air into the work area or move air from inside the work area to
outside the building. Fresh air in the latter case will come through other openings in the building. The use of
portable fans placed in the work area can also be considered dilution ventilation, though they are not typically
as effective. An example using the metalworking operation would be to place large fans in the ceiling above
the machines and blow fresh air through the area, reducing the employees’ exposure to metalworking fluids.
In many cases, the use of dilution ventilation is adequate to reduce exposures to an acceptable risk level.

LEV systems collect the air at the source and move it somewhere else through duct systems. Where the
contaminated air is moved depends on how it will be treated. Sometimes the air is simply discharged to the
outside air. Other contaminants require some type of treatment, such as filtration or disintegration. Whether
the air can be released directly to the outside air or needs some type of collection or treatment will depend on
the specific compound. Some chemicals are too toxic to release into the outside air directly, and some states
have regulations controlling the release of specific chemicals from a facility. An example using the
metalworking fluid operation is to place an LEV above or near the machine to collect and filter out aerosols
associated with the fluids. This type of LEV is commonly called a smog hog by industry. Another example of
using an LEV would be laboratory fume hoods commonly found in laboratory settings. Although called fume
hoods, they typically are used for gases and vapors, not fumes.

The next level of controls on OSHA’s Hierarchy of Controls is administrative and work practice controls.
These do not provide the level of controls that engineering controls can, but may further reduce residual risk if
the engineering controls cannot reduce the residual risk to an acceptable level. Administrative controls can
reduce risk by limiting the amount of time an employee spends in a certain area. Let’s say a certain task
requires work near a machine that produces constant noise levels exceeding 100 dBA. The first approach
would be to apply some type of sound barrier to reduce the exposure. If this was not possible, employees
could be rotated into and out of the area to limit their total exposure to a point below the OSHA PEL and
action level.

Work practice controls could also be used to evaluate the standard operating procedures used by employees,
and then work practices could be changed to reduce exposures. For example, if a job has been performed

4

UNIT x STUDY GUIDE

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during the first work shift, and there is an unacceptable risk of heat illness in the summer, the work could be
moved to the third shift during periods of lower temperatures to reduce the risk.

Reference

Occupational Safety and Health Administration. (n.d.). Basic hazard awareness [PowerPoint slides].
Retrieved from https://www.osha.gov/dte/grant_materials/fy10/sh-20839-
10/basic_hazard_awareness.pptx

Suggested Reading

To access the following resources, click on the links below:

Implementing engineering controls for some occupational noise sources may prove difficult. The following
article evaluates the use of a fairly simple engineering control method for reducing noise during tire
manufacturing operations.

Cockrell, W. T., Jr., Balanay, J. A. G., & Dawkins, W. (2015). Engineering case reports: Engineering control of
noise from 4-roll calender operations in tire manufacturing. Journal of Occupational and
Environmental Hygiene, 12(9), D193–D200. Retrieved from
https://libraryresources.waldorf.edu/login?auth=CAS&url=http://search.ebscohost.com.libraryresource
s.waldorf.edu/login.aspx?direct=true&db=aph&AN=109017162&site=ehost-live&scope=site

The construction industry sometimes presents unique problems for ventilation systems. There are some
commercially available LEV systems for tools used in the construction industry. The following article evaluates
a commercially available LEV used for cutting roof tiles containing crystalline silica.

Garcia, A., Jones, E., Echt, A. S., & Hall, R. M. (2014). Case study: An evaluation of an aftermarket local
exhaust ventilation device for suppressing respirable dust and respirable crystalline silica dust from
powered saws. Journal of Occupational and Environmental Hygiene, 11(11), D200–D207. Retrieved
from https://libraryresources.waldorf.edu/login?url=https://doi.org/10.1080/15459624.2014.955182

Diacetyl is a chemical that has received much press coverage because of serious health effects in workers at
microwave popcorn factories. Sometimes when new manufacturing processes and health hazards are
discovered, new engineering controls have to be invented. The article below discusses engineering controls
developed by researchers at NIOSH for diacetyl operations at a microwave popcorn manufacturing facility.

Hirst, D. V. L., Dunn, K. H., Shulman, S. A., Hammond, D. R., & Sestito, N. (2014). Evaluation of engineering
controls for the mixing of flavorings containing diacetyl and other volatile ingredients. Journal of
Occupational and Environmental Hygiene, 11(10), 680–687. Retrieved from
https://libraryresources.waldorf.edu/login?auth=CAS&url=http://search.ebscohost.com.libraryresource
s.waldorf.edu/login.aspx?direct=true&db=bxh&AN=BACD201400496422&site=ehost-live&scope=site

OSHA sometimes publishes requirements for ventilation in regulations. The following document contains links
to several regulations discussing ventilation requirements.

Occupational Safety and Health Administration. (n.d.). Ventilation: Possible solutions. Retrieved from
https://www.osha.gov/SLTC/ventilation/solutions.html

The following OSHA document contains a summary of control methods for noise hazards. It also contains
links to other web sites with information about noise controls and some case studies.

Occupational Safety and Health Administration. (n.d.). Occupational noise exposure: Exposure and controls.
Retrieved from https://www.osha.gov/SLTC/noisehearingconservation/evaluation.html

https://online.waldorf.edu/CSU_Content/Waldorf_Content/ZULU/EmergencyServices/OSH/OSH4301/W16Gc/UnitVIIReading1

https://online.waldorf.edu/CSU_Content/Waldorf_Content/ZULU/EmergencyServices/OSH/OSH4301/W16Gc/UnitVIIReading1

https://libraryresources.waldorf.edu/login?url=https://doi.org/10.1080/15459624.2014.955182

https://online.waldorf.edu/CSU_Content/Waldorf_Content/ZULU/EmergencyServices/OSH/OSH4301/W16Gc/UnitVIIReading2

https://online.waldorf.edu/CSU_Content/Waldorf_Content/ZULU/EmergencyServices/OSH/OSH4301/W16Gc/UnitVIIReading2

https://www.osha.gov/SLTC/ventilation/solutions.html

https://www.osha.gov/SLTC/noisehearingconservation/evaluation.html

5

UNIT x STUDY GUIDE
Title

Learning Activities (Nongraded)

Non-graded Learning Activities are provided to aid students in their course of study. You do not have to
submit them. If you have questions, contact your instructor for further guidance and information.

There are several free sound level meter applications (apps) for smartphones available on the Internet.
Download one of the apps, and use it to measure the sound levels, in dBA, of some noise sources around
your home and workplace. Do any of the readings surprise you? Which sources were high enough that you
would be concerned about hearing loss?

Basic Hazard Awareness

“This material was produced under the grant SH-20839-SHO from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.”

Objectives
By the end of this workshop, you will:
 
Identify how workplace injuries or illnesses can affect your everyday life.
Identify common symptoms, aches/pains, illnesses and injuries that are associated with your work.
Identify and recognize the exposures and hazards linked to work-related illnesses and injuries.
Develop solutions and strategies to address these identified hazards.

CHEMICAL & DUST HAZARDS
(cleaning products, pesticides, asbestos, etc.)
BIOLOGICAL HAZARDS
(mold, insects/pests, communicable diseases, etc.)
ERGONOMIC HAZARDS
(repetition, lifting, awkward postures, etc.)
WORK ORGANIZATION HAZARDS
Things that cause STRESS!
SAFETY HAZARDS
(slips, trips and falls, faulty equipment, etc.)
PHYSICAL HAZARDS
(noise, temperature extremes, radiation, etc.)

3

Hierarchy of Controls
Requires a physical change to the workplace
Requires worker to wear something
Elimination/Substitution
Requires worker or employer to do something
Most Effective
Least Effective

These are referred to as the hierarchy of controls, how you prevent or control a hazard:
Elimination/Substitution: The main goal for any fix to a hazard or exposure is to eliminate it altogether or substitute a product or method of doing the work to a less hazardous alternative. (e.g. green cleaning products)

4

CONTROLS: Engineering
CONTROL AT THE SOURCE!
Limits the hazard but doesn’t entirely remove it.
Local Exhaust
Other Examples:
Mechanical Guards
Wet Methods for Dust
Enclosures/Isolation
Dilution Ventilation
Proper equipment
Re-designed Tools
Image: by Kare_Products
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The basic concept behind engineering controls is that, to the extent feasible, the work environment and the job itself should be designed to eliminate hazards or reduce exposure to hazards. While this approach is called engineering controls, it does not necessarily mean that an engineer is required to design the control. Engineering controls are the “first line of defense” against injury/illness, because they have the potential to completely eliminate a hazard, and do not rely on human behavior to be effective. For instance, rather than require employees to wear respiratory protection which must be monitored, inspected, trained, managed, it’s much more effective to install a ventilation system that does not require any of those management activities or, better yet, find an alternative substitute that is less hazardous.

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CONTROLS: Administrative
Aimed at Reducing Employee Exposure to Hazards but Not Removing Them!
Changes in work procedures such as:
Written safety policies/rules
Schedule changes, such as:
Lengthened or Additional Rest Breaks
Job Rotation
Adjusting the Work Pace
Training with the goal of reducing the duration, frequency and severity of exposure to hazards

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Administrative controls (or work practice controls) are changes in work procedures such as written safety policies, rules, supervision, schedules, and training with the goal of reducing the duration, frequency, and severity of exposure to hazardous chemicals or situations.
As with work practice controls, administrative controls normally are used in conjunction with other controls that more directly prevent or control exposure to hazard.
Image: Powerpoint Clipart

CONTROLS: PPE
Personal Protective Equipment
Control of LAST RESORT!
Special Clothing
Eye Protection
Hearing Protection
Respiratory Protection
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CONTROL IS AT THE WORKER!

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Personal protective equipment (PPE): A method that prevents a worker from being exposed to the hazard by something the worker wears (e.g., gloves, hardhat, of safety glasses). PPE is considered the method of last resort because PPE does nothing to reduce or eliminate the hazard. If the PPE fails, immediate exposure is the result. Examples of PPE include:
 
a.   Special clothing: like gloves, aprons, boots, coveralls, etc.
 
b.   Eye protection: like safety glasses or face shields
 
c.   Hearing protection
Respiratory protection: for emergency or short-term protection.
Images: all from OSHA website

Hierarchy of Controls
Requires a physical change to the workplace
Requires worker to wear something
Elimination/Substitution
Requires worker or employer to do something
Most Effective
Least Effective

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OSHA STATE PLAN STATES

This map shows that our public employee members in 27 states enjoy the same OSHA rights as all workers in the private sector. They have a legal right to a safe and healthy workplace.
 
All public employers in the 27 OSHA states are required to follow OSHA standards. When they are not in compliance, workers and their unions have the right to file a complaint and receive an inspection if they feel that their working conditions are unsafe.
 
But, the map also shows that there are millions of public workers in the rest of the states that have no OSHA protection. Unfortunately, any type of protection for public employees in non-OSHA state plan states are spotty at best.
 
Even with OSHA coverage … many of the hazards we are exposed to everyday don’t have standards that address them.

Image: Pamela Wolfe, AFT
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OSHA Asbestos Standard
Applies in all 50 states for school employees
Provides protection for custodians and maintenance workers who must remove or handle asbestos as part of their duties.
OSHA also protects any school employee in any state who is harassed or discriminated against for complaining about asbestos exposure.

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Image: by Beige Alert’s photostream
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Valuable resource for information on all types of hazard exposures
Can conduct Health Hazard Evaluations (HHE) if requested by union or members

The National Institute for Occupational Safety and Health (NIOSH), the research arm of OSHA is another valuable resource for information on hazard exposures. They can also come into workplaces and do Health Hazard Evaluation (HHE) if requested by the union or members in response to a hazard exposure.
Images: NIOSH
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OSHA 300 Log of Injuries and Illnesses
Employer must post all work-related injuries and illnesses that result in a day or more away from work.
You have a right to request copies and/or see log.

Employer must post a summary of these logs each year from February 1 – April 30.

Required in the 27 state plan states that cover public employees. This is a model for what should be required for all workplaces.
Image: OSHA PDF
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