At first glance the physiological demands of the firefighter, the scuba diver and the hospital patient have little in common. One is trained to deal with fire and rescue, one swims underwater and one is concerned with either regaining or improving their health. Yet all three depend to some extent on a safe source of compressed breathing air, which is where our gas detection systems come in.
In the case of the firefighter, portable breathing sets enable them to work in dangerous atmospheres that would otherwise prove fatal. In the aquatic environment the self-contained underwater breathing apparatus of the scuba diver allows mobility in the ocean depths. And many hospital patients benefit from the use of compressed breathing air in both medical breathing systems and surgical procedures.
All of these applications employ the same fundamental technology: an air compressor and a collection of portable air tanks or fixed storage vessels. Ambient air is drawn into the compressor from the local environment and filtered as it enters to remove any airborne impurities. At the point of delivery—or before it is stored in cylinders for distribution—the compressed breathing air is periodically tested to ensure it is free from contaminants.
Fire stations and diving companies often refill their own breathing air cylinders using a compressor. Many factories and hospitals use the same process to supply breathing air via a fixed distribution network. Under optimum atmospheric conditions, this is effective but any local air pollution entering the compressor—such as vehicle exhaust fumes or industrial emissions—has a profoundly detrimental effect on the end product.
Compressed breathing air can be contaminated with carbon monoxide (CO) or volatile organic compounds (VOCs) if these are in the atmosphere. Other risks include oxygen (O2) depletion resulting from leakage of an inert gas such as nitrogen (N), or hazardous levels of carbon dioxide (CO2) released by concentrated sources in the vicinity (e.g. dry ice). A poorly maintained compressor could itself produce a toxic oil mist.
The UK British Standards Institution recommends a quarterly air test in its document ‘BS EN 12021:2014 Respiratory equipment. Compressed gases for breathing apparatus’. This test is usually performed by a specialist sub-contractor using colorimetric tubes to conduct a ‘spot check’ of the air quality. These checks provide chemical analysis of the air and are an essential part of any maintenance programme.
Quarterly spot checks, however, can only provide a snapshot of the air quality at the time of the test. Any deficiencies that are inherent in the system may be highlighted but intermittent problems resulting from occasional environmental pollution could be overlooked. It was the recognition of this potential hazard, i.e. toxic gas contamination in breathing air, that led to Analox developing the ACG+ range of gas sensors for monitoring compressed breathing air.
The ACG+ multi-gas analyser for compressed breathing air safety
The Analox ACG+ is a multi-sensor gas analyser that checks the levels of O2, CO2, CO, VOC, oil mist and dew point (humidity). It is specifically designed for the analysis of contaminants in compressed breathing air and it delivers a much greater degree of safety than a quarterly spot check. It provides continuous monitoring of O2, CO2, CO, volatile organic compounds (VOC) and water vapour in compressed breathing air lines.
The ACG+ can either be used as a portable instrument for testing different compressors or be permanently connected to a single compressor outlet. It retains datalogs for 90 days and allows them to be downloaded via USB to a computer. Live gas measurements are taken every 10 seconds – which means that in the three months between spot checks or laboratory tests an ACG+ could have logged more than 700,000 readings, providing continuous real-time results, and therefore ensuring round the clock breathing air safety at all times.
Author: Paul Smith, Technical Writer