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 https://www.osha.gov.

                  Regional Administrator

                  ARA for Technical Support

THRU:             JOHN B. MILES, JR.
                  Director Office of Field Coordination

                  Acting Director
                  Federal Compliance and State Programs

SUBJECT:          Del-Monox Air Purifiers

This is in response to your memorandum of September 4, 1981, concerning the possible use of the color change feature of Del-Monox air purifying units to ensure that carbon monoxide concentrations stay within the OSHA air quality requirement for breathing air supplied by oil-lubricated compressors.

The legal procedures for ensuring that the carbon monoxide concentration in breathing air supplied by oil-lubricated compressors stays within the OSHA specification are contained in 29 CFR 1910.134[(i)(7)], which reads, in part, as follows:


If only a high-temperature alarm is used, the air from the compressor shall be frequently tested for carbon monoxide to insure that it meets the specifications in paragraph (d)(1) of this section.


(Correction 11/24/98)

[For oil-lubricated compressors, the employer shall use a high-temperature or carbon monoxide alarm, or both, to monitor carbon monoxide levels. If only high-temperature alarms are used, the air supply shall be monitored at intervals sufficient to prevent carbon monoxide in the breathing air from exceeding 10 ppm.]

OSHA interprets this provision to entail a requirement to measure the concentration of carbon monoxide in the air. The Del-Monox air purifying units to which you refer in your memorandum do not perform this function.

An employer who wants to use the color change feature of the Del-Monox air purifying units instead of frequently testing the air, would have to apply for and obtain a permanent variance from the Office of Variance Determination in the Directorate of Technical Support.