The provision of breathable air to be used by a person in the execution of a work related task is controlled by certain legal requirements
BS EN 12021:1999 is the standard in the UK which sets out the permitted levels of contaminants in compressed air that is used for breathing through respiratory protective devices.
Compressed air for breathing shall not contain contaminants at a concentration which can cause toxic or harmful effects. In any event all contaminants shall be kept to as low a level as possible, and shall be below the limits as set down in BS EN 12021:1999
The substances that are tested are as follows:-
Carbon monoxide
Oxygen
Carbon dioxide
Oil mist
Water vapour
The quality of the air supplied for breathing should be tested at least every three months and more frequently when the quality of the air supply cannot be assured.