Airborne Contaminants

Chapter 296-841, WAC

Effective Date: 04/01/07

Helpful Tools

WAC 296-841-200

Evaluate and control employee exposures

For printing

WAC 296-841-20003

Employee protective measures

WAC 296-841-20005

Exposure evaluations

WAC 296-841-20010

Exposure controls

WAC 296-841-20015


WAC 296-841-20020


WAC 296-841-20025

Permissible exposure limits (PELs)


WAC 296-841-20003

Protect employees from potentially hazardous exposure while you perform your exposure evaluation, using all available resources to determine adequate protective measures.



Resources include product labels, material safety data sheets (MSDSs), manufacturer recommendations, and industry protocols.


WAC 296-841-20005

Exposure evaluations

You must

(1) Conduct an exposure evaluation to determine or reasonably estimate whether an employee is or could be exposed to either of the following:

  • An airborne contaminant above a permissible exposure limit (PEL) listed in Table 3;


  • Other airborne hazards, such as biological hazards.


  • When evaluating air contaminants, keep in mind that oxygen deficient conditions may also occur due to:

    – Processes such as fermentation, decomposition of organic matter, or combustion of fossil fuels

    – Displacement by another gas such as nitrogen or carbon dioxide

  • Rules for specific substances may contain additional requirements for determining employee exposure
  • Samples from a representative group of employees may be used for other employees performing the same work activities, when the duration and level of exposure are similar.

(2) Conclude that an atmosphere is immediately dangerous to life or health (IDLH) when you cannot determine or reasonably estimate employee exposure.

(3) Do all of the following when you perform your evaluation:

(a) Determine the form of the airborne contaminant, such as dust, mist, gas, or biological agent.

(b) Make sure you do not use the amount of protection provided to employees by respirators as a factor in determining whether employees are exposed to an airborne hazard.

(c) Make sure any air monitoring results used to determine employee exposures are based on personal air samples taken from, or representative of, the employee’s breathing zone.

  • You may use area sampling to screen for the presence of an airborne contaminant; however, results from area sampling cannot be used if they do not adequately represent exposure of affected employees.

(d) Include potential emergency and rescue situations that may occur, such as equipment or power failures, uncontrolled chemical reactions, fire, explosion, or human error.

(e) Include workplace conditions such as work processes, types of material, exposure control methods, work practices, and environmental conditions.

(f) Address extended work periods. For work shifts longer than 8 hours, evaluate the continuous 8-hour portion of the shift expected to have the highest average exposure concentration.

(4) Use either of the following types of documentation to conclusively demonstrate that employee exposure cannot meet or exceed any PEL for the airborne contaminant during any reasonably anticipated conditions:

  • – Personal air samples that represent an employee’s usual or worst-case exposure during the entire shift.
  • or
    – Specific information about products, materials, or activities that provide for an estimate of the level of employee exposure such as material safety data sheets (MSDSs), observations, previous air sampling results, other measurements, calculations, or pesticide labels.


You should use methods of sampling and analysis that have been validated by the laboratory performing the analysis.

(5) Use the following formula to evaluate employee exposure to 2 or more substances that have additive health effects:

The symbol Is the . . .
E Equivalent exposure for the mixture. When the value of E is greater than 1, an airborne hazard is present.
C Concentration of a specific airborne contaminant.
L TWA, STEL, or ceiling for that substance, from Table 3, Permissible Exposure Limits (PELs) for Airborne Contaminants
Helpful Tool

Helpful Tool:

Mixtures of Airborne Substances

Use this instruction to find out if health effects of contaminants are additive and if added exposures represent an airborne hazard.



  • When results from your exposure evaluation indicate an airborne hazard, follow requirements in WAC 296-841-20010 through 296-841-20020 of this chapter.
  • When changes occur that increase the level of exposure to an airborne hazard, you may need to conduct a new exposure evaluation to make sure exposure controls and other protective measures are sufficient.

WAC 296-841-20010

Exposure controls


  • Respirators and other personal protective equipment are not exposure controls. Respirators may be used to protect employees while exposure controls are being installed or when it is not feasible to use exposure controls to remove or reduce the airborne hazard.

(1) Use feasible exposure controls to reduce employee exposure to one of the following:

  • - A level below the permissible exposure limits (PEL) in Table 3.
  • - A level that removes the airborne hazard, when no PEL is established.
  • - The lowest achievable level, when exposure cannot be reduced to below the PEL or the airborne hazard cannot be removed.

(2) Make sure exposure controls do not create or increase employee health hazards. For example, when ventilation systems are installed.

  • - Prevent contaminated exhaust air from either:
      • Reentering the building in harmful amounts
      • Exposing any employee to a health hazard.

  • - Temper make-up air, when necessary
  • - Prevent employee exposure to excessive air velocities.

(3) Use make-up air systems that will not interfere with the effectiveness of the exhaust air system.

  • - For example, make sure enough make-up air is provided to replace the amount of air exhausted.


  • Table 1 provides examples of possible exposure controls.

Table 1
Examples of Possible Controls

Preferred exposure controls include:

For example:

Using a different chemical (this is also known as substitution)

  • Choose a chemical with a lower evaporation rate or vapor pressure
  • Choose a chemical that's not hazardous

Changing a process to decrese emissions

  • Use hand rolling or paint dipping instead of paint spraying
  • Bolt items instead of welding them

Separating employees from emissions areas and sources

  • Use control rooms
  • Build an inclosure around process machinery or other emissions sources
  • Automate a process

Using local exhaust ventilation to remove emissions at or near the source

  • Install exhaust hoods or slots to capture emissions
  • Use an exhausted enclosure (like a blasting cabinet or laboratory hood)

Other exposures controls include:

For example:

Using general exhaust ventilation to dilute and remove emissions in the work area


This is not recommended for control of highly toxic airborne contaminants such as carcinogens, where low exposures can still present a health hazard

  • Allow natural air movement to create an adequate airflow through an area
  • Use mechanical fans

Limiting the amount of time employees can spend in a contaminated area

  • Establish a contaminant-free area for tasks such as prep work that do not need to be done in the exposure area

Modifying work practices

  • Change the position of the employee relative to the work so fumes, vapors, or smoke are not directed into the employee's face

Implementing an employee rotation schedule

  • Have employees alternate working in the exposure area so that each employee gets less overall exposure


WAC 296-841-20015


  • Require employees to use respirators when airborne hazards haven’t been removed using feasible exposure controls. For example, use respirators at any of the following times:
  • – While exposure controls are being evaluated or put in place

    – When the airborbne hazard isn’t completely removed

    – When exposure controls are not feasible.


    See chapter 296-842 WAC, Respirators, for respirator program requirements.

WAC 296-841-20020


• Notify employees who are, or may be exposed to airborne hazards, as specified in Table 2.



  • The notification may be provided either individually, to a group, or by posting of results in an appropriate location that is accessible to affected employees.


Table 2
Notification Requirements

Notify employees of

As follows

Any exposure result above a permissible exposure limit (PEL)

Within 5 business days, after the employee's exposure result is known to the employer

The corrective action taken to reduce employee exposure to or below the PEL and

The schedule for completion of the corrective action and any reasons why exposures cannot be lowered to below the PEL

Within 15 business days, after the employee's exposure result in known to the employer

WAC 296-841-20025

Permissible exposure limits (PELs)


The following information applies to Table 3, Exposure Limits (PELs) for Airborne Contaminants.

  • Ppm refers to parts of vapor or gas per million parts of air by volume, at 25° C and 760 mm Hg pressure.
  • (Mg/m3) refers to milligrams of an airborne contaminant per cubic meter of air.
  • F/cc refers to fibers per cubic centimeter of air.
  • For a metal that is measured as the metal itself, only the CAS number for the metal is given. The CAS numbers for individual compounds of the metal aren’t provided. For more information about CAS registry numbers see the website:
  • Short-term exposure limits (STEL) pertain to 15-minute exposure periods, unless another time period is noted in Table 3.
  • An “X” in the “skin” column indicates the contaminant can be absorbed through the skin, either by airborne or direct contact.
    • – Personal protective equipment (PPE) to prevent skin contact may be needed to minimize the risk for adverse health effects when employees are exposed to these chemicals.

    • – Requirements for the use of gloves, coveralls, goggles, and other personal protective equipment can be found in WAC 296-800-160, Personal protective equipment (PPE).

  • Nuisance dusts (also known as inert dusts) are included in the Table 3 listing, particulates not otherwise regulated (PNOR).
  • – The PNOR listing in Table 3 also applies to other particulate airborne contaminants for which a specific PEL IS NOT listed unless the airborne contaminant is found to require a lower limit.

  • The respirable fraction of particulate is airborne contaminant is measured by sampling with a size-selector having the following characteristics:


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