Peak-above-ceiling exposure limit

Peak-above-ceiling exposure limit The short-term exposure peak permitted above the OSHA standard ceiling exposure level. 

OSHA PEL. The permissible exposure limit is measured on a normal 8 h day over a 40 h per week for an average worker, called the time-weighted average (TWA). Other important parameters are CL, which indicates the ceiling limit that must not be exceeded, and Pk, which designates the maximum peak value allowed, which is above the ceiling value. 

The final OSHA Benzene standard in 1910.1028 applies to all occupational exposures to benzene except some subsegments of industry where exposures are consistently under the action level (i.e., distribution and sales of fuels, sealed containers and pipelines, coke production, oil and gas drilling and production, natural gas processing, and the percentage exclusion for liquid mixtures) for the excepted subsegments, the benzene limits in Table Z-2 apply (i.e., an 8-hour TWA of 10 ppm, an acceptable ceiling of 25 ppm, and 50 ppm for a maximum duration of 10 minutes as an acceptable maximum peak above the acceptable ceiling). 

An employee s exposure to material listed in OSHA Table Z-2 shall not exceed at any time during an 8-h shift the acceptable ceiling concentration limit given for the material in the table, except for a time period, and up to a concentration not exceeding the maximum duration and concentration allowed in the column under Acceptable Maximum Peak Above the Acceptable Ceiling Concentration for an Eight-Hour Shift. ... 

OSHA lists an acceptable ceiling concentration of 20 ppm for hydrogen sulfide. The acceptable ceiling concentration is the exposure limit that shall not be exceeded at any time during an 8-hour shift. Hydrogen sulfide has an exception in that it has an acceptable maximum peak above the acceptable ceiling concentration of 50 ppm for an 8-hour shift as long as the maximum duration is once for 10 minutes, and only if no other measurable exposure occurs [2]. 

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