Standard Interpretations - Table of Contents
• Standard Number: 1910.430(b)(4)

October 9, 1985

               Area Director, Baltimore


FROM:          LINDA R. ANKU
               Regional Administrator

SUBJECT:       Interpretation of 29 CFR 1910.430(b)(4)

This is in response to your written inquiry of September 17, 1985 (copy attached) which requested interpretation of 1910.430(b)(4) which states that the output of air compressor systems shall be tested for air purity every 6 months by means of oil samples taken at the connection to the distribution system. The exception is that non-oil lubricated compressors need not be tested for oil mist.

Some employers and other compressor users feel that testing for air purity is not necessary when air is properly filtered at the intake and the compressor uses a non-hydrocarbon lubricating oil. Perusing the attached reports from Texas Research Institute, it is apparent that a filter at the compressor inlet does an adequate job of establishing air quality to acceptable standards. However, there is no uniform filter maintenance schedule that is followed by all compressed air suppliers and there is no standard for distance away from the compressor to areas containing exhaust and other contaminants. Also, a substantial percentage of air compressors are driven by gasoline engines exposing the air to internal combustion engine contaminants.

Even when the compressor uses Monolec oil, satisfactory air quality cannot be obtained when the filters are not maintained properly. (See attached letter dated August 20, 1985 from Lubrication Engineers, Inc. to McLean Contracting Company. The Lebanon, PA