Permissible Exposure Limits

Our Laboratory Safety Plan is intended to limit laboratory workers' exposure to OSHA (Occupational Safety and Health Administration)-regulated substances.

The plan sets a threshold for exposure: lab workers must not be exposed to substances in excess of the permissible exposure limits (PEL) specified in OSHA rule 29 CFR 1910, Subpart Z, Toxic and Hazardous Substances or threshold limits values set by the American Conference of Governmental Industrial Hygienists.

PELs are airborne concentrations of substances averaged over an eight-hour day. A few substances also have action levels  -- levels or air concentrations that are below the PEL but that require actions, such as medical surveillance and workplace monitoring.


Guidance: Pay particular attention to the following paragraph. If you, as a lab supervisor or Laboratory Safety Officer, suspect exposure concentrations exceed allowable levels, please contact the Department of Risk Management and Safety for technical assistance.


If there is reason to believe an employee's workplace exposure will exceed an action level or a PEL, this exposure must be monitored. In addition, if exposures to any regulated substance routinely exceed action levels or permissible exposure levels, control measures are required.

A. Professional Judgement

The lab supervisor can use professional judgment to assess the nature of chemical exposure resulting from a lab procedure and prescribe engineering controls and personal protective equipment to be used during the procedure. This judgment will be documented through use of Standard Operating Procedures and Laboratory Chemical Safety Summaries written for the chemicals in use.

B. Air Sampling

Air sampling for evaluating employee exposure to chemical substances shall be conducted on an as needed basis (to be determined by the lab supervisor). Conduct air sampling if there is reason to believe that exposure levels for regulated substances that require sampling routinely exceed the action level, or in the absence of an action level, the PEL.

Air sampling will be conducted according to established industrial hygiene practices. It may be conducted by lab workers, Risk Management and Safety staff or outside consultants. The results of air sampling studies performed in the laboratory should be sent to the Risk Management and Safety Department for records maintenance.