Without prejudice to the occupational exposure limit values laid down in articles R. 4222-10, R. 4412-149 and R. 4412-150, the air or mixtures breathed during work must have the following characteristics:
1° In the case of carbon dioxide, a partial pressure of less than 10 hectopascals ;
2° In the case of carbon monoxide, a partial pressure of less than 0.05 hectopascals;
3° In the case of water vapour, for exposures lasting more than 24 hours, a relative humidity of between 60 per cent and 80 per cent;
4° In the case of oil vapours, a partial pressure expressed as methane equivalent of less than 0.5 hectopascal and a concentration of less than 0.5 mg/m³.
The density of a breathing mixture must not exceed 9 grams per litre at the working pressure.