Hot Cold Tube de Bullard

Hot cold tube

The requirements for Grade D breathable air include:
Oxygen 19.5-23.5%
Hydrocarbons (condensed) in mg/m3 of gas 5 mg/m3 max.
Carbon monoxide 10 ppm max.
Carbon dioxide 1,000 ppm max.
Odor No detectable odor
No toxic contaminants at levels that make air unsafe to breathe.