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When? What? How Much?
Employers must characterize the nature and magnitude of employee exposures to
respiratory hazards before selecting respiratory protection equipment. Paragraph
(d)(1)(iii) of the final rule requires the employer to identify and evaluate the respiratory hazard(s) in the
workplace. Employers must make a "reasonable estimate" of the employee exposures
anticipated to occur as a result of those hazards, including those likely to be encountered in reasonably
foreseeable emergency situations, and must also identify the physical state and chemical form of such
contaminant(s). The final rule does not specify how the employer is to make reasonable
estimates of employee exposures for the purposes of selecting respirators.
When must an employer conduct an exposure assessment?
When you expose your employees to a respiratory hazard and/or require them to wear
respirators. Examples of when you should consider assessments may include but are not limited to:
What is the identity and nature of the airborne contaminant?
Specific characteristics of the airborne hazard must be established in order to select an
- When OSHA has a substance specific standard (e.g., lead, methylene chloride).
- When employees notice symptoms (e.g., irritation, odor) or complain of respiratory health effects.
- When the workplace contains visible emissions (e.g., fumes, dust, aerosols).
How much employee exposure is there in the workplace?
The final rule permits employers to use many approaches for estimating worker exposures to
- Is the airborne contaminant a particulate (dust, fumes, mist, aerosol) or a gas/vapor?
- Is the airborne contaminant a chemical and are material safety data sheets available?
- Is the airborne contaminant a biological (bacteria, mold, spores, fungi, virus)?
- Are there any mandatory or recommended occupational exposure levels for the contaminant?
- Sampling - Personal
exposure monitoring is the "gold standard" for determining employee exposures
because it is the most reliable approach for assessing how much and what type of
respiratory protection is required in a given circumstance.
- Sampling should utilize methods appropriate for contaminants(s).
- Sampling should present the worst case exposures; or
- Sampling should represent enough shifts and operations to determine the range of exposure
- Objective Information -
You may rely on information and data that indicate that use or handling of a product or
material cannot, under worst-case conditions, release concentrations of a respiratory
hazard above a level that would trigger the need for respirator use or require use of a
more protective respirator.
- You can use data on the physical and chemical properties of air contaminants, combined
with information on room dimensions, air exchange rates, contaminant release rates, and
other pertinent data, including exposure patterns and work practices, to estimate the
maximum exposure that could be anticipated in the workplace.
- Data from industry-wide surveys by trade associations for use by their members, as well
as from stewardship programs operated by manufacturers for their customers, are often useful
in assisting employers, particularly small-business owners, to obtain information on employee
exposures in their workplaces.
- Variation - You should
account for potential variation in exposure by using exposure data collected with a
strategy that recognizes exposure variability, or by using worst-case assumptions and
estimation techniques to evaluate the highest foreseeable employee exposure levels. The
use of safety factors may be necessary to account for uneven dispersion of the contaminant
in the air and the proximity of the worker to the emission source.