Employers responsible for environments that require respiratory protection must ensure that exposed workers breathe good, clean air. According to OSHA Standard 29 CFR 1910.134, employers are required to provide employees who use respirators with breathing air that meets the requirements for Grade D breathing air.
Grade D breathing air, as described in ANSI/Compressed Gas Association Commodity Specification for Air, G-7.1-1989, includes the following1: