The OSHA Respiratory Protection Standard 1910.134 requires employers to "identify and evaluate the respiratory hazard(s) in the workplace". While it does require the employer to perform an evaluation, it does not require a specific method, other than it being a "reasonable estimate" of employee exposure. The employer needs to decide the best way to assess employee exposure levels. There are many options available to employers. When selecting a method, it is important that you document everything in writing.
Personal Monitoring
The most accurate way to determine exposure is to perform personal monitoring. This involves the use of badges, air collection pumps, and other devices to track the level of exposure in a work area. While this is the best method, it may be beyond the capabilities or resources of smaller employers. Fortunately, OSHA does permit other options.
Note: Some regulations, like asbestos, require personal monitoring for determining exposure levels.
Location Monitoring
The employer can monitor fixed locations, or collect samples for short time periods. If this method is used, the employer should perform samples under the worst-case exposure scenarios, to make sure that the assigned level of protection is adequate for all conditions.
Data from Previous Exposure Measurements
There may be data available from product manufacturers, trade associations, or other organizations that document expected exposure levels. If this data is used, the conditions in the workplace must match the conditions in the survey.
Consult with an Industrial Hygienist
Employers with dangerous hazard profiles should consider bringing in a safety and health professional to determine exposure levels. OSHA consultation programs may also be able to help employers determine exposure levels.
Assume IDLH If Levels Cannot Be Determined
If the employer cannot make a reasonable estimate of exposure levels, they must assume that the atmosphere is immediately dangerous to life and health (IDLH), and provide the requisite protection.
References
- 29 CFR 1910.134 - Respiratory Protection
- Atmospheric Hazard Assessment Letter of Interpretation
- Respiratory Protection - Small Entity Compliance Guide