Breathing air from compressors: your responsibilities

If your staff wear air fed masks, hoods or breathing apparatus connected to a compressor, that compressor is no longer just plant. It is a life critical supply. Ordinary compressed air is not safe to breathe, and the law expects you to prove that the air reaching each wearer is.

What the law requires

COSHH Regulation 9

Regulation 9 of the Control of Substances Hazardous to Health Regulations 2002 (COSHH) covers the maintenance, examination and testing of control measures. Respiratory protective equipment (RPE) must be kept in efficient working order and good repair, and reusable RPE must be thoroughly examined and, where appropriate, tested at suitable intervals. Records of those examinations and tests must be kept for at least five years.

The COSHH Approved Code of Practice (HSE publication L5) adds that air supplied to breathing apparatus should be tested at suitable intervals and meet the relevant quality standard, with your risk assessment guiding which other contaminants to test for.

HSG53 and BS EN 12021

HSE’s guide HSG53, Respiratory protective equipment at work, names the standard. Air supplied to breathing apparatus from a compressor should meet BS EN 12021, Respiratory protective devices: Compressed air for breathing apparatus, as well as the pressure and flow requirements of the equipment manufacturer.

HSG53 says testing frequency should be based on risk assessment, but at least every three months, and more often when air quality cannot be assured. Mobile compressors may need testing each time they are moved. Air quality test records should be kept for five years.

Some industries have tighter sector guidance. HSE’s bodyshop guidance for isocyanate paint spraying, for example, recommends more frequent checks of breathing air lines. Check the guidance that applies to your own work.

Remember too that the compressor, receiver and pipework are a pressure system in their own right. Our PSSR 2000 guide explains the separate written scheme and examination duties.

What BS EN 12021 sets out

The overriding principle is that breathing air must not contain any contaminant at a level that could be toxic or harmful, and all contaminants should be kept as low as possible. The current 2014 edition sets specific limits, including:

• Oxygen: 21%, plus or minus 1%
• Carbon monoxide: no more than 5 ml/m³ (5 ppm)
• Carbon dioxide: no more than 500 ml/m³ (500 ppm)
• Oil: no more than 0.5 mg/m³
• Water: no free liquid water. For compressor supplied air, the pressure dewpoint should be at least 5°C below the lowest likely temperature, or no higher than minus 11°C where that temperature is not known
• Odour and taste: the air should be free of any significant odour or taste

Different limits apply to air compressed into high pressure cylinders, so tell your test provider how the air is used.

The contaminants that matter

Carbon monoxide

Carbon monoxide (CO) is the most dangerous because it has no smell and no taste, so the wearer gets no warning. It can be drawn in from vehicle exhausts, generators, heaters and flues, or created inside an oil lubricated compressor running too hot. Standard filters and dryers do not remove it.

Carbon dioxide

Carbon dioxide (CO2) normally comes in with the intake air. High readings point to exhaust fumes, poor ventilation or a nearby process.

Oil

Lubricated compressors put oil into the air as liquid, aerosol and vapour. Degraded or overheated oil is worse. Oil mist in the lungs is a real hazard, and oil vapour is a common source of odour.

Water, odour and particles

Wet air is uncomfortable to breathe, can freeze valves and encourages bacterial growth in hoses. Odour or taste usually means something else is getting through. Rust, scale and dirt from pipework must also be filtered out.

Why a standard compressor needs dedicated purification

A factory compressor with a refrigerant dryer and general filters produces air that is fine for tools and machinery. It is not breathing air. A dedicated breathing air purifier is fitted between the supply and the breathing air outlets. A typical unit combines:

• Coalescing filters to remove liquid water, oil aerosol and particles
• A desiccant stage to dry the air to the required dewpoint
• Activated carbon to remove oil vapour, odour and taste
• A catalyst that converts carbon monoxide into carbon dioxide
• A final dust filter, with pressure regulation to suit the breathing equipment

An oil free compressor does not remove the need for purification. It still draws in whatever is in the surrounding air, including carbon monoxide and hydrocarbons.

Label breathing air outlets clearly and use couplings that cannot be confused with other supplies such as nitrogen. We supply, install and service breathing air purifiers, filters and carbon monoxide monitors.

Carbon monoxide monitoring

A quarterly test only shows what the air was like on the day. Carbon monoxide can rise at any time: a lorry idling near the intake, or a compressor running hot with a blocked cooler. A continuous CO monitor with an alarm, fitted where purified air enters the breathing line, warns wearers to stop and leave the area. Calibrate it as the manufacturer specifies.

Siting the compressor intake

HSG53 says compressor air inlets should be sited in free air, away from the work area and upwind of local sources of contamination such as vehicle exhaust. In practice, keep the intake away from:

• Loading bays, car parks and forklift charging or refuelling areas
• Generators, boiler flues and heater exhausts
• Spray booth and extraction discharge points
• Solvent and chemical stores

Review the intake position whenever the site layout changes, and every time a mobile compressor is set up in a new place.

Testing and record keeping

HSG53 lists acceptable test methods: colour change tubes, online gas testers, or samples sent for laboratory analysis. Test at the point where the breathing hose connects, not only at the purifier, so that the pipework is included in the result.

A good record shows the date, sample point, each result against the BS EN 12021 limit, who tested and any action taken. Keep it with your RPE examinations, filter and catalyst changes, CO monitor calibration and compressor servicing history. If an inspector asks, that file is your evidence.

Who typically needs breathing air

• Spray booths: HSE states that filtering respirators are not suitable for spraying isocyanate paints, so sprayers need air fed equipment.
• Shot and abrasive blasting: operators work inside air fed blasting helmets.
• Confined spaces: tanks, vessels and pits where the atmosphere cannot be made safe.
• Chemical and pharmaceutical handling: tasks where hazardous substances cannot be controlled at source.

Frequently asked questions

Can I use my existing workshop compressor for breathing air?

Often, yes, provided it has the capacity, a well sited intake and a dedicated purifier with carbon monoxide protection. The air must then be tested against BS EN 12021.

How often does breathing air need testing?

HSE guidance in HSG53 says at least every three months, and more often if your risk assessment shows the quality cannot be assured. Some sector guidance asks for more frequent checks.

Does an oil free compressor produce breathable air?

No. It avoids adding compressor oil, but it still draws in carbon monoxide, carbon dioxide, water and other contaminants from the surrounding air. Purification and testing are still required.

How long should I keep test records?

COSHH requires records of RPE examinations and tests to be kept for at least five years, and HSG53 recommends the same for air quality test results.

J&J Air Systems has worked with compressed air since 1963. We are ISO 9001 and ISO 14001 certified, BCAS members, and our engineers cover London and the Home Counties from High Wycombe. If you supply breathing air from a compressor and want your setup checked, contact us to talk it through.