In some industrial sectors the ambient atmospheric air is too contaminated for operatives to breathe safely. Andy Lill, business development manager for Quality Air at Atlas Copco, discusses the role of compressed air purification as a safe alternative to contaminated air.
When we talk of safe alternatives to contaminated air, the emphasis must be on ‘safe’ and it is important that the risks are fully understood. Standard compressed air is generally insufficient to ensure consistent breathing air quality and it is vital for everyone to realise that untreated compressed air is not clean.
The compression of ambient air concentrates the normal contaminants already present in the air and can also introduce other constituents such as oil vapours, condensed water and bacteria that can have an immediate negative effect on operators’ well-being and long-term health.
Air purifiers The solution to the problem is the addition of breathing air purification equipment to the compressed air supply, controlled and monitored in accordance with compressed air for breathing quality standards such as EN 12021:2014 'Respiratory equipment. Compressed gases for breathing apparatus'.
When selecting the appropriate purification equipment, it must be remembered that contaminates will be in one of three states of matter: solid, liquid or gaseous. The corresponding contaminant limits within EN 12021:2014 requirements are as follows: • Odour: the gas shall be free from unsatisfactory odour and taste • Oxygen: content shall be 21% +/- 1% • Carbon dioxide: content shall be less than 500 ppm • Carbon monoxide: content shall be less than 5 ppm • Oil: content shall be less than 0.5 mg/m3 • Water (for airlines less than 40 BarG): where the apparatus is used and stored at a known temperature the compressed breathing air shall have a dew point sufficiently low to prevent condensation and freezing and be at least 5°C below the likely lowest temperature. Where the conditions of usage and storage of any compressed air supply is not known, the pressure dew point shall not exceed -11°C.
Purity levels In order to limit the health risk and comply fully with regulatory requirements, it is essential that assured purity levels are achieved by the purification unit within the compressed air network. The ideal breathing air purifier should have the capacity to take air from any type of compressor and convert it into ultra-clean breathing quality air. It needs to combine the functions of water separation, contaminant filtration and desiccant drying of the air output.
One such unit, Atlas Copco’s breathing air purifier (BAP) range, features seven vital functions: a water separator that removes any liquid water, a bulk aerosol filter to eliminate oil and water content, a fine coalescing filter to remove even smaller particles of oil and water from the supply, plus a desiccant dryer to take out any remaining water and CO2. An activated carbon filter is included to remove gaseous impurities and a catalyst takes care of CO oxidation. Finally, a bacteria filter eliminates micro-organisms and fine particles.
This level of capability ensures the breathing air purifier complies with a wide range of standards and regulations, such as OSHA Grade D, NFPA-99, CSA Z180.1-00, CGA G7.1-1997, EN 12021, BS 4275, ISO 14971, OHSAS 18001, European Pharmacopeia and other international breathing standards. Such compliance guarantees a safe working environment in a wide range of applications, ranging from shot-blasting, tank cleaning, tunnelling, pharmaceutical manufacturing, spray painting, offshore/marine processes, asbestos removal, to high-pressure cylinder filling and many others.
Testing Within a purified compressed air supply network, it is essential to carry out air quality tests to ensure that the control measures put in place are delivering the air quality required. In the UK, 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 any concerns relating to, the production process.
The Health and Safety Executive (HSE) guideline document, 'Respiratory protective equipment at work' (HSG53) states that the frequency of such tests should be based on a risk assessment, should take place at least every three months and more often when the quality of air cannot be assured to these levels.
For mobile breathing-air compressors in the UK, the 'Control of Substances Hazardous to Health (COSHH) 2002' stipulates that the employer should ensure that, wherever a compressor is located, the quality of the air it supplies is not compromised by nearby contaminants. It strongly recommends that for mobile compressors the air quality is tested whenever the unit is first moved into a new position or if prevailing wind conditions change.
The final decision on frequency of tests is the responsibility of the employer and needs to not only reflect local legislation but also the task and frequency of use. It should be incorporated into risk assessments and updated regularly to reflect results from ongoing breathing air tests in order to maintain a robust control system. Legal requirements EN12021:2014 is now the standard to indicate contaminant levels for breathing air both in the UK and in the EU, expressed as: “in any event all contaminants shall be kept to as low a level as possible and shall be below the national exposure limit“, but the following guides may help employers to further understand the specific regulations as they apply to a variety of industry requirements: • 'The Management of Health and Safety at Work Regulations 1999' (SI 1999/3242) requires a safe working environment through the application of risk assessment procedures. • 'The Personal Protective Equipment Regulations 2002' (SI 2002/1144) Schedule refers to the design and manufacturer of respiratory protective equipment. • 'The Work in Compressed Air Regulations 1996 '(SI 1996/1656) deal with those aspects where the user is operating in a pressure higher than atmospheric, e.g. tunnelling. • 'Control of Substances Hazardous to Health (COSHH) Regulations' 2002 (SI 2002/2677) and amended by S.I. 2004 No. 3386 in respect of the term "workplace exposure limit"). These regulations identify the maximum exposure limits for a defined list of contaminants which may be present in a workplace atmosphere.
Exposure limits The exposure limits are now identified by the single term, "workplace exposure limit (WEL)" which encompasses both long- and short-term exposure. Related to COSHH is a reference listing published annually under the EH40 Occupational Exposure Limits. The listings are in addition to those in COSHH. Where any doubt exists about the limits for any contaminant then this should be used as a starting point.
It goes without saying that only competent personnel should be involved in designing breathing air systems and preparing risk assessments. To assist employers in this complex area of health and safety, it is recommended that managements seek the assistance of compressed air system suppliers with specific breathing air capabilities and product ranges, such as Atlas Copco, who will have competent persons trained in providing and maintaining breathing air systems.