Why breathing air is a separate purchase
Ordinary plant air is judged by whether tools and processes work. Breathing air is judged by whether a person can breathe it safely for a full shift, often inside a blast helmet, a confined space or a contaminated area where they cannot simply remove the mask. The hazards are different: carbon monoxide, oil mist and vapour, water, particles, odour, and too little or too much oxygen. Some of these give no warning to the wearer.
For that reason a breathing-air system should be bought as a life-safety system with a named owner, a defined standard and documented acceptance tests. The compressor is one component in that system.
Which application and which standard?
Different uses have different rules. Decide which one applies before anyone asks for quotations.
| Application | Typical arrangement | Points that set the specification |
|---|---|---|
| Supplied-air respirators for blasting, painting and coating | Compressor or plant air through a breathing-air purifier to air-fed hoods or masks | Air quality standard named by the client, CO monitoring, hose length and pressure at the hood |
| Confined space and tank entry | Air line with escape cylinder or trolley-mounted cylinder bank | Escape reserve, alarms, supervision, permit-to-work |
| Fire service and SCBA cylinder filling | High-pressure breathing-air compressor, typically about 200–300 bar | Cylinder approvals, high-pressure purification, filling station safety |
| Diving | Low- or high-pressure diving compressor with purification | Diving regulations and standards, competent dive supervisor |
| Medical air for patients | Medical gas pipeline system | Medical gas standards and hospital approvals; outside general breathing-air practice |
Commonly referenced breathing-air quality standards include EN 12021 in Europe and Grade D air under CGA G-7.1 in the United States. ISO 8573-1, the general compressed-air purity standard, describes particle, water and oil classes but does not by itself define breathing air, because it does not set limits for carbon monoxide, carbon dioxide or odour. The client, its safety adviser and the regulations that apply to the site decide which standard governs; the specification should name it and its edition.
The full chain from intake to mask
Specify every element, because a weakness anywhere reaches the wearer.
- Air intake: located away from engine exhausts, vehicle routes, generator sets, paint booths and process vents. A diesel portable compressor drawing its own exhaust is a classic carbon monoxide source.
- Compressor: oil-free or oil-injected, with temperature protection. An overheated oil-lubricated compressor can produce carbon monoxide from oil breakdown.
- Aftercooler and moisture separation to remove bulk water.
- Air receiver sized to give a reserve if the compressor stops.
- Breathing-air purifier: coalescing filters for oil aerosol, a dryer stage, activated carbon for oil vapour and odour, and a catalyst stage for carbon monoxide where specified.
- Monitoring: continuous CO monitor with alarm, and where required oxygen, dew point and pressure alarms.
- Distribution: dedicated, labelled breathing-air lines with couplings that cannot be connected to plant air or other gases.
- Point of use: pressure regulation and flow suited to the respirator maker’s approved range, and an escape supply where the work requires one.
How do I stop carbon monoxide getting into breathing air?
Carbon monoxide is the most dangerous contaminant because it cannot be seen, smelt or felt until symptoms appear. It reaches breathing air in two main ways: the compressor draws in exhaust gas, or the compressor itself generates CO when oil overheats.
- Site the intake upwind of and well away from any engine exhaust, and keep the diesel compressor’s own exhaust away from its intake.
- Where possible use an electric compressor for breathing air, or a separate dedicated unit, rather than the site’s blasting compressor.
- Keep compressor discharge temperature within the normal range; for an oil-injected screw this is typically about 75–95 °C, and a high-temperature trip must work.
- Fit a continuous CO monitor downstream of the purifier, with an audible and visual alarm at the work position.
- Use a CO catalyst in the purifier where the risk assessment calls for it, and replace it on schedule.
Responsibilities: who owns what
Disputes and incidents often come from unclear boundaries. Write them down before ordering.
| Role | Usually responsible for |
|---|---|
| Client or site owner | Choosing the application and standard, risk assessment, permits, competent supervision, final acceptance |
| Breathing-air specialist or purifier supplier | Purifier selection, monitoring, test method, certification of air quality where required |
| Compressor supplier (our role) | Compressor and air source of suitable capacity and condition, aftercooling, receivers, service of the air source |
| Respirator supplier | Respirator approval, inlet pressure and flow range, training and fit testing |
| Contractor or user | Daily checks, alarm response, correct couplings, filter changes as instructed |
Capacity and pressure for air-fed respirators
Each hood or mask needs a set airflow at a set pressure, given by the respirator maker. Add up the users, allow for hose losses and the purifier’s pressure drop, and add a reserve. For blasting, remember that the blast nozzle takes far more air than the operator: a No. 6 nozzle at 7 bar (101.5 psig) typically uses about 280–300 cfm, while one blast hood takes only a small fraction of that. That is why a separate, smaller, clean air source for breathing is often the safer and simpler design than tapping the blast compressor.
Specify the receiver and escape reserve so that if the compressor stops, every wearer has time to leave the hazard safely. The time needed is set by the client’s risk assessment, not by the compressor supplier.
Comparing bids
Bids for “breathing-air compressors” are rarely like-for-like. Before comparing price, check that each one answers the same questions:
- Which air-quality standard and edition does the offer claim to meet, and at which point: compressor outlet or mask?
- Is a continuous CO monitor included, with alarm at the work position?
- Which purifier stages are included, and what are the cartridge change intervals and indicators?
- What flow and pressure are available at the end of the stated hose length for the stated number of users?
- What testing is offered at commissioning, and by whom?
- Which couplings prevent cross-connection to plant air or other gases?
- What training, documents and service schedule come with the system?
Acceptance testing and ongoing checks
- Check the installation against the drawings: intake position, purifier, monitors, couplings and labels.
- Run the system at full user load and confirm pressure and flow at the furthest point of use.
- Have air quality sampled at the point of use by a competent tester, for the parameters of the named standard.
- Test every alarm and the escape reserve.
- Record results, filter and cartridge installation dates, and handover training.
- Repeat air-quality testing at the interval required by the standard or site rules, and after any major change or repair.
Maintaining the air source
A breathing-air system is only as safe as its last service. The compressor and its treatment need a written schedule, kept by someone named, with records the safety adviser can inspect.
- Inlet filter condition and intake surroundings checked before each shift, especially on construction and blasting sites where exhausts move.
- Oil level, oil condition and discharge temperature on oil-injected machines; overheating is a carbon monoxide risk, not just a reliability issue.
- Aftercooler cleanliness and automatic drains working, so water does not overload the purifier.
- Purifier cartridges and CO catalyst changed by the maker’s schedule or indicator, never stretched.
- CO monitor calibration and alarm tests as the maker specifies.
- Couplings, hoses and labels inspected for damage and cross-connection risk.
How Reddy Compressors helps
We supply, rent and service compressors that a breathing-air specialist can use as the air source: oil-free and oil-injected compressors, aftercoolers, receivers, dryers and filtration, as an independent multi-brand specialist working across ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and others, not an authorised dealer. We have tie-ups with all major and reputed brands. For blasting and coating contractors we can supply rental air for the blast nozzles and discuss a separate clean air source for operators.
The breathing-air purifier, CO monitoring, air-quality certification and respirator approval remain with the client’s breathing-air specialist and safety adviser; we work alongside them and make sure the compressor side is suitable and well maintained. Our service teams, based at Tarnaka, Secunderabad, cover all of Telangana and Andhra Pradesh, and we supply equipment across India.
What to send us
- The application: blasting, painting, confined space, cylinder filling or other.
- The air-quality standard your client or safety adviser has named.
- Number of users, respirator type and the maker’s flow and pressure range.
- Hose lengths and site layout, including engine exhaust locations.
- Power available on site and whether diesel or electric is preferred.
- Details of any existing compressor and purifier, with nameplate photos.
Frequently asked questions
Is oil-free compressed air safe to breathe?
Not automatically. Oil-free compression removes lubricating oil from the compression chamber, but the air can still contain carbon monoxide drawn in from exhausts, water, particles, odour and oil vapour from the surroundings. Breathing air needs proper intake siting, purification, continuous CO monitoring and testing to a named standard before anyone can rely on it.
Can I use my blasting compressor to supply air to the blaster’s helmet?
It is possible only through a proper breathing-air purifier with CO monitoring, and with the intake and exhaust arranged so the compressor cannot draw in its own fumes. Many contractors prefer a separate, smaller electric or dedicated compressor for breathing air, which is simpler to control. Your safety adviser should approve the arrangement.
What standard applies to compressed breathing air?
The client and the site’s regulations decide. Commonly referenced standards include EN 12021 in Europe and Grade D air under CGA G-7.1 in the United States. ISO 8573-1 alone is not a breathing-air standard because it does not set limits for carbon monoxide, carbon dioxide or odour. The specification should name the standard and its edition.
How does carbon monoxide get into compressed air?
Mainly in two ways. The compressor intake can draw in exhaust from its own engine, a generator or vehicles nearby. Or an oil-lubricated compressor running too hot can break down its oil and produce CO internally. Correct intake siting, temperature protection, a CO catalyst where required and a continuous CO alarm guard against both.
How often should breathing air be tested?
At commissioning, then at the interval set by the governing standard and site rules, and again after any repair, incorrect filter change or system modification. Continuous monitors for carbon monoxide and, where required, other parameters give live protection between laboratory tests. Keep records of every test and cartridge change.
Who is responsible for breathing-air quality?
The employer or site owner holds overall responsibility, supported by a competent breathing-air specialist who selects purification and testing. The compressor supplier is responsible for a suitable, well-maintained air source. The respirator supplier sets the flow and pressure range. Writing these boundaries into the purchase order prevents gaps that put wearers at risk.
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Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.