Breathing Air Filling
Q: What is Grade D air?
A: OSHA requires all supplied air respirators, including SCBA, use Grade D or better air. Better air is defined as E or F. The specifications in the U.S. for Grade D air are described in ANSI/Compressed Gas Association (CGA) Commodity Specification for Air, G-7.1-1989, and in Canada in CSA Standard Z180.1.
OSHA specifications include:
• Oxygen (O2) content a minimum of 19.5% and a maximum of 23.5% per volume
• Hydrocarbon (condensed) content of 5 mg/m3 or less
• Carbon Monoxide (CO) content of 10 ppm or less
• Carbon Dioxide (CO2) content of 1,000 ppm or less
• Lack of a noticeable odor
• The moisture content in the cylinder may not exceed a dew point of -50˚ F (-45.6˚ C) at 1 atmosphere pressure.
CSA Standards Information is available here.