Zu "grade D" schon mal :
What is Grade-D Air Quality?
Breathing air quality standards have been developed by ANSI /
Compressed Gas Association (CGA) G-7.1 - 1989, and adopted by
OSHA under their respiratory standard 29 CFR, 1910.134.
Air Quality Must Meet or Exceed The Following Requirements:
• Oxygen: 19.5%-23.5% (20%-22% Canada)
• Hydrocarbon (condensed oil) 5 mg/m3 maximum (<1Mg/m3 in Canada)</i>
• Carbon Monoxide (CO): 10 ppm maximum (5 ppm in Canada)
• Carbon Dioxide (CO2): 1000 ppm maximum (500 ppm in Canada)
• Odor: No noticeable tastes or smells
• Water Content:
High pressure cylinder air must have a dew point of at least -50° F
(-45.6° C) at 1 atmosphere (14.7 psi).
Low pressure breathing air must have a dew point of at least 10° F
C) below the ambient temperature at 1 atmosphere (14.7 psi)
Canada: 5° C below lowest temperature, 27 ppm maximum water vapor
• Total Volatile Hydrocarbons (Canada): 5 ppm maximum