A recent incident at a Fire Department in Henderson, Nevada, prompted emergency action and a hefty bill for city officials. Firefighters reported a smell of petroleum coming from the air tanks in their self-contained breathing apparatus (SCBA). The problem was traced to an air compressor which is believed to have introduced contaminants into the system. The compressor has now been replaced, together with the hoses and nozzles, and the air tanks have been cleaned. Precautionary toxicology tests and chest x-rays for the firefighters pushed the final cost to $138,000.
Most fire stations refill their own air cylinders using a compressor. This takes in air from the local environment and pressurises it for use as a breathing gas. The air is filtered on its way through the system to remove any impurities, thus preventing contamination. Under normal conditions this is an effective process but any local pollution from vehicle exhausts and industrial emissions can have a profound effect on air quality. Compressor intakes must therefore be located away from contaminants, and regular equipment maintenance and air testing are essential.
The dangers of toxic gas contamination in SCBA are well-known. Compressed breathing air has been known to include raised levels of carbon monoxide (CO) which is a dangerous gas, and hydrocarbons (VOCs) which are potentially toxic. The atmospheric gases such as oxygen, carbon dioxide and nitrogen are safe at normal levels but any change in concentration may be hazardous. Oil mist can be produced by a leaking compressor and could cause chemical pneumonia. Even water vapour, if present in sufficient quantity, may lead to corrosion in air systems and can also cause components to freeze.
According to ‘14 News’, the US media organisation that first reported the story on 26 March 2015, Henderson Fire Department has now implemented a quarterly air analysis and equipment check for its compressed breathing air system. This fits the recommendations of the National Fire Protection Association, which requires at least a 3-monthly air sampling schedule (‘NFPA 1404: Standard for Fire Service Respiratory Protection Training’). The UK British Standards Institution also recommends a 3-monthly test in ‘BS EN 12021:2014 Respiratory equipment. Compressed gases for breathing apparatus’.
Analysis of compressed breathing air involves difficult gas monitoring techniques usually facilitated by a specialist laboratory or a niche gas detection company. Appropriate gas sensors have historically been prohibitively expensive and complicated to use. Consequently compressed breathing air is often implicated in dangerous incidents, not only in firefighting air systems but also in SCUBA compressors which supply air to divers. In a similar case to the Henderson incident, West Yorkshire Fire & Rescue Service in the UK recently noted a problem with contaminants entering the compressors they use to refill firefighters’ breathing air tanks. Following discussions with Analox, West Yorkshire bought an ACG+ multi-sensor gas analyser, specifically designed for the analysis of contaminants in compressed breathing air.
The ACG+ is a fixed or portable gas sensor which continually monitors oxygen, carbon dioxide, carbon monoxide, volatile organic compounds and dew point in the breathing air produced by the compressor. It also includes a port which is used to run an oil-mist test. It can be used either continuously or periodically to verify whether or not the air is safe, and its portability makes it ideal for situations employing multiple compressors or sites. In contrast to colorimetric tube or laboratory testing of air (both are costly, and only provide a spot check) the ACG+ logs data every 10 seconds. Its continuous monitoring regime highlights any contamination or variation in gas levels at an early stage, thus allowing corrective measures to be taken. The ACG+ can also be maintained by the user, has low running costs and is simple to calibrate and use.