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Safety & Lifesaving
Breathing Air Systems
Breathing Air Systems covers high-pressure breathing air compressors and filtration, cascade storage, airline systems, self-contained breathing apparatus (SCBA) and emergency escape breathing devices for H2S and fire response.
Compressors and cascades are machinery that can be overhauled and reused. Cylinders carry a test date and a service life, and the air itself must meet a written quality standard.
How a breathing air system works
A high-pressure compressor draws air from a clean intake, compresses it in three or four stages and pushes it through filtration. The filter train removes water, oil and particles. Activated carbon removes odour and some hydrocarbons, and a catalyst such as hopcalite converts carbon monoxide to carbon dioxide. Clean air fills SCBA cylinders through a filling panel or charges a cascade bank. The cascade then supplies airline respirators or tops up cylinders. On sour wells, an airline system lets crews work for long periods in H2S without cylinder changes.
Configurations
| Item | Purpose | Main standard |
|---|---|---|
| Breathing air compressor | Fills cylinders and cascades | Air quality to EN 12021 or CGA G-7.1 |
| Cascade bank | Stores air for filling or airline supply | Pressure vessel rules for the cylinders |
| SCBA | Open circuit set for rescue, firefighting and H2S | EN 137, NIOSH approval, NFPA 1970 (formerly NFPA 1981) for fire service |
| Airline respirator | Long-duration work on a supply hose | EN 14593-1 |
| Escape set | Time-limited escape from H2S or smoke | EN 402; FSS Code Chapter 3 for EEBDs |
EN 137 divides SCBA into Type 1 for industrial use and Type 2 for firefighting. Emergency escape breathing devices (EEBDs) under the FSS Code give at least 10 minutes of air.
Key specifications
| Parameter | Why it matters | Typical classes or units |
|---|---|---|
| Filling pressure | Must match cylinders and panels | 200 or 300 bar (about 3,000 or 4,500 psi) |
| Compressor delivery | Sets how fast cylinders refill | L/min or scfm free air |
| Cylinder type and volume | Sets duration and weight | Steel, aluminium or composite; water litres |
| Valve thread and connection | Decides compatibility | EN 144 or CGA connections |
| Ex rating | Compressors in hazardous areas | Zone rating on motor and controls |
Air quality standards
EN 12021 sets oxygen at 21 ± 1%, carbon monoxide at no more than 5 ppm, carbon dioxide at no more than 500 ppm and oil at no more than 0.5 mg/m³. It also limits water content according to the fill pressure and use temperature. CGA G-7.1 Grade D, which OSHA cites for US workplaces, has looser limits. Test the air at the filling point at the interval your quality plan sets and after any filter change or overhaul.
Cylinder life and requalification
- Steel and aluminium cylinders need periodic inspection and a hydrostatic test at the interval their approval sets.
- Composite cylinders made to EN 12245 are marked with a service life or as non-limited life (NLL).
- In the US, carbon composite SCBA cylinders are made under DOT special permits that usually limit service life to 15 years from manufacture. Some later permits allow extension after acoustic emission testing. That 15-year figure is a US rule, not an EN 137 requirement.
- A cylinder past its test date or life must not be filled, whatever its condition.
Failure modes and inspection
- Compressor. Check hours since overhaul, interstage pressures, valve condition, condensate drains and safety valves.
- Filtration. Check the cartridge change record against the hour meter, and the CO monitor alarm.
- Cascades. Check cylinder test dates, manifold leaks and relief valves.
- SCBA. Check the mask seal, demand valve, pressure reducer, warning whistle and gauge. Run a positive pressure and leak test on the maker's test bench.
Documentation
- Compressor running hours, overhaul records and the last air quality test certificate.
- Cylinder test dates, serial numbers and manufacture dates.
- SCBA service records from an authorised service centre, with part numbers of every replaced component.
- Approval certificates for the SCBA model and its configuration.
Integration
Match cylinder pressure, valve thread and quick couplings to your existing sets. SCBA approval covers the whole set as tested, so mixing cylinders, masks or demand valves from different makers can void it. Site a compressor intake where exhaust, mud gas and H2S cannot reach it.
Refurbishment and what never to buy used
A compressor or cascade can return to service after an overhaul, new filters, a relief valve test and an air quality test. Used SCBA is worth considering only with full service history and cylinders well within life. Never buy escape sets with a broken seal, cylinders past their test date or life, or filter cartridges of unknown age.
For gas monitoring during entry, see portable gas detectors.
FAQ
Frequently asked questions
What air quality standard applies to breathing air on a rig?
EN 12021 applies under European rules and CGA G-7.1 Grade D under US OSHA rules. EN 12021 limits carbon monoxide to 5 ppm, carbon dioxide to 500 ppm and oil to 0.5 mg/m³. Your operator may set the stricter of the two.
How long do composite SCBA cylinders last?
It depends on the cylinder's approval, so read its label. In the US, DOT special permits usually limit carbon composite cylinders to 15 years from manufacture. EN 12245 cylinders carry a stated life or are marked non-limited life (NLL).
Can I mix SCBA parts from different makers?
No, SCBA approval to EN 137 or NIOSH covers the set as tested, with its own cylinder, mask and demand valve. Swapping components from another maker can void the approval. Keep each set to the configuration on its certificate.
What should I check on a used breathing air compressor?
Check hours since overhaul, interstage pressures, safety valve settings and the filter change record first. Then run it and test the air at the filling point against EN 12021 or Grade D. Confirm the CO monitor alarms.
Can a used escape breathing device be reused?
Usually not, because most escape sets are sealed units and a broken seal or tripped indicator means they must go back for service. Buy them unused, with the seal intact and the maker's service date in hand.
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