Substances with No Established RELs

At that time, NIOSH also conducted a limited evaluation of the literature and concluded that the documentation cited by OSHA was inadequate to support the proposed PEL (as an 8-hour TWA) of 10 mg/m for the compounds listed below. The current PEL for magnesium oxide fume is 15 mg/m (8-hour TWA, total particulate), and the eurrent PEL for molybdenum (insoluble eompounds as Mo) is 15 mg/m (8-hour TWA, total dust). For the other eompounds listed below the eurrent PEL is 15 mg/m (8-hour TWA, total dust) and 5 mg/m (8-hour TWA, respirable dust). 

Employees engaged in handling operations involving the carcinogens listed below must be provided with, and required to wear and use, a half-mask filter-type respirator for dusts, mists, and fiimes. A respirator affording higher levels of protection than this respirator may be  

Firefighting Self-contained breathing apparatus with full facepiece in positive-pressure mode. 

Escape (1) Any organic vapor respirator or (2) Any self-contained breathing apparatus. 

Requirements for Respiratory Protection for Inorganic Arsenic Particulate Except for Those With Significant Vapor Pressure 

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