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FAC QAM 190 Issue D 09/18
Appendix 5 - Air Quality Testing – Why?
The required quality of breathing air is stated in EN12021 is to provide information on the safe limits
of potential contaminant gases within breathing air and to ensure that the life support gas of oxygen
is of an adequate level.
Compressed air for breathing normally originates from a compressor system installed or operating at
the place of use and there are various factors that can affect the quality and safety of this air.
The air intake to the compressor can ingest airborne contamination from local processes and
vehicle exhaust fumes which are not removed by standard breathing air filtration. Such air borne
contamination may not be continuous but the pollution of the air supply may persist for hours or
days.
Malfunctioning compressors, especially reciprocating type, can produce unsafe levels of both
carbon monoxide and carbon dioxide.
Breathing air filtration has a finite life and can fail causing high levels of oil and water
contamination to be present in the air.
The performance of desiccant filters is dramatically affected by operating temperature.
Infrequent validation may result in poor quality air being supplied for an extended period
Failure of the compressed air aftercooling will result in air entering the filtration at too high a
temperature, this will cause the filtration to prematurely fail and pass excess levels of oil and
water.
Malfunctioning dryers can disturb the oxygen concentration to outside safe levels within the
breathing air.
High levels of water in breathing air can freeze within RPD demand valves causing the air supply to
fail.
Insufficient air flow or pressure to the RPD will reduce the protection factor of the RPE and
potentially expose the user to ingress of external contaminants.
The effects of contaminants when breathed at elevated pressure can have a much greater effect
on users than it would at normal pressure.
Changes in the performance of compressor and filtration equipment are usually rapid in nature.
Any failure affecting outlet air quality may injure users for an extended period if quality validation
is infrequent.
Odour alone is a poor indicator of air quality, toxic as asphyxiant gasses are often odourless, the
limits for oil pollution are lower than the threshold detection level that most people will notice.
All employers have a duty of care to their employees to ensure that the breathing air they are
supplied with is adequate for the RPD they are using and safe to breathe. The points raised above
may form the basis of the risk assessment called for in the European guidance document for the
selection and use of respiratory protective devices EN 529.
