Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

June 21, 1988

Mr. Andrew P. Szilagyi
Project Manager
ICF Technology Incorporated
9300 Lee Highway
Fairfax, Virginia 22031-1207

Dear Mr. Szilagyi:

This is a followup to our interim response to your inquiry of May 13, concerning the use of direct reading instruments to comply with the monitoring requirements in the Hazardous Waste Operation and Emergency Response interim final rule (29 CFR 1910.120).

OSHA agrees that direct reading instruments are primary tools for initial site characterization. They are allowable as long as they provide the necessary information to determine appropriate protection measures (e.g., personal protective equipment, evacuation) during site activities. Thus, 29 CFR 1910.120(c)(4)(IV) and (h)(1) which you referenced can be interpreted, as appropriate, to mean the establishment of the presence and concentration of specific chemicals or classes of chemicals and other health hazards.

After hazardous waste cleanup operations commence, ongoing monitoring may be necessary. Employee exposure to any health hazards that exceed established permissible exposure limits (PEL's) must be quantified. (Representative sampling as defined in 29 CFR 1910.120(h)(4) is allowable.) Qualitative sampling methods are acceptable as the sole means for ongoing air monitoring when exposures to health hazards do not exceed established PEL's and the methods can detect all particularly toxic agents. Where necessary, routes of exposure other than inhalation must be monitored.

You also addressed an additional question with our staff concerning the acceptability of objective data instead of monitoring when employee exposures are below established PEL's. In general, OSHA would consider objective data as an acceptable method to characterize employee exposure under the interim final rule when maximum employee exposures are not expected to exceed one-half of any established PEL. The objective data must be well documented and include the use of safety factors. The results of employee exposure characterization by objective data must be made available upon request to affected employees according to 29 CFR 1910.1020. In cleanup operations where many complex factors combine to influence employee exposure to hazardous substances and other health hazards objective data would not be appropriate.

I hope this information is helpful. If I can be of further assistance, please let me know.


John A. Pendergrass
Assistant Secretary