High pressure breathing compressed air for firefighters.

Pure compressed air for self-contained breathing apparatus

RAF Lakenheath houses the 48th Fighter Wing, with its operations, medical, maintenance and mission support groups. The military base is run and operated by the US Air Force, it exclusively hosts American troops. The 48th CES firefighters train routinely to remain proficient in their response to emergencies.  Cambs Compressors supply and maintain breathing air compressors for the 48th CES fire fighters. This produces pure clean breathing air for use in their self-contained breathing apparatus (SCBA). The reason firefighters work with compressed air and not oxygen in their tanks is because oxygen tanks could explode in a fire.

RAF Lakenheath is located in Suffolk, and the installation is a co-base run by the Americans under the British regulations and laws. It’s also referred to as the Liberty Wing, and was first activated on site in 1952. It represents one of the longest lasting units in the Air Force, serving in the area for almost 60 years. The wing counts almost 8000 individuals. About 2000 of them are British civilians and family members, while almost 6000 are active military troops.

The importance of breathing air quality, testing, regulations and standards

Regular maintenance and quality testing of compressed air for breathing is essential. There are various factors that can affect the quality and safety of compressed air for breathing. All employers have a duty of care to their employees to ensure that the breathing air they are supplied with is adequate for the respiratory protective devices (RPD) they are using and are safe to breathe.

Breathing air quality risks, and risk assessments

The points raised below 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

• Breathing air filtration has a finite life and can fail, causing high levels of oil and water contamination to be present in the air.
• 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.
• 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 the reciprocating type, can produce unsafe levels of both carbon monoxide and carbon dioxide.
• 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 after cooling 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.
• 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.

In the UK national forward to EN12021 advises that samples should be taken and analysed at least every three months or more frequently if there has been a change in, or concerns relating to, the production process.

In the HSE guideline document Respiratory Equipment at Work (HSG53) it states you should base the frequency of such tests on a risk assessment, but again, they should take place at least every three months, and more often when the quality of air cannot be assured to these levels.

High pressure breathing compressed air

Whilst up to a 3 month periodicity for testing may be suitable for low pressure breathing-air systems, further consideration should be given to high pressure compressors where the life of filter elements are normally much shorter, typically 50 hours for a HP filter cartridge and this is reduced further in high ambient temperatures.