OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at http://www.osha.gov.

November 13, 1989

Mr. Rob J. Lee
Division Manager
400 Mann Street, Room 300
Corpus Christi, Texas 78401

Dear Mr. Lee:

This is in response to your letter to the Corpus Christi Area Office of the Occupational Safety and Health Administration (OSHA) concerning monitoring employee exposures to airborne benzene.

Your company's practice of providing its employees with personal respiratory protection devices does not relieve it of the requirement to monitor its employees exposures to airborne benzene. This is so even though your company has assumed the worst conditions of benzene exposure and provides the most highly protective respirators required.

The conditions for terminating the monitoring of employee exposures to 8-hour, time-weighted average (TWA) concentrations of benzene are provided in the benzene standard at 29 CFR 1910.1028(e)(4). In short, 29 CFR 1910.1028(e)(4) relates that this monitoring cannot be terminated until employee exposures are maintained consistently below an 8-hour TWA benzene concentration of 0.5 parts per million (ppm).

The standard does not provide specific conditions for terminating the monitoring of employee exposures to 15-minute TWA concentrations of benzene. Our compliance policy is to accept termination of this monitoring when the results of the monitoring demonstrate that employee exposures do not exceed the short term exposure limit (STEL) of 5 ppm.

You should be aware that employee exposure is defined at 29 CFR 1910.1028(b) as "exposure to airborne benzene which would occur if the employee were not using respiratory protective equipment." OSHA was aware of outside exposure situations when it issued the standard. The agency concludes that employers can do a good evaluation of outside employee exposures by notating the environmental conditions and other factors that influence each exposure result.

Moreover, the benzene standard requires employers to inform each of their employees of their levels of exposure to airborne benzene and to provide the same information to the physician conducting the medical surveillance program. Please refer to 29 CFR 1910.1028(e)(7)(i) and (i)(6)(iii). In addition, the standard requires employers to post warning signs at the entrances to regulated areas, that is, areas where employees will be overexposed to benzene if they remain there. Please refer to 29 CFR 1910.1028(d) and (j)(1)(i). Employers would be unable to comply with these requirements if they did not monitor the airborne benzene concentrations.

I appreciate the opportunity to clarify this matter for you. If you need further information please do not hesitate to contact me.


Thomas J. Shepich, Director
Directorate of Compliance Programs