Compressor, Air Quality, and Gas Supply Systems
Air is a breathing gas, not utility air
The exam tests whether the compressor and gas supply system can deliver clean, breathable gas at the required purity. Inspectors check intake location, filtration, maintenance, monitoring, and testing. Breathing air should meet the adopted purity standard, commonly CGA Grade E where that grade is specified; oxygen-compatible systems require oxygen cleaning and dedicated components.
System controls
- Compressor intake located away from exhaust, engine fumes, and confined spaces.
- Carbon monoxide monitoring with calibrated sensors and alarms.
- Filter and separator maintenance at defined intervals, with records.
- Air quality sampling at defined intervals and after any event that could contaminate the system.
- Cylinder filling procedures, including fill rate and cooling.
- Gas analysis and labeling for mixed gas; no unlabeled cylinders.
- Cascade and bank systems with pressure relief and isolation.
Worked example
A compressor intake sits beside a diesel generator exhaust. The carbon monoxide monitor alarms during a fill. The operator changes the filter and continues. Reasoning: the filter is not the source control; the intake is. Continuing without stopping the fill, relocating the intake, and retesting the air exposes divers to contaminated gas. The correct action is to stop filling, isolate the affected cylinders, investigate, and verify air quality before returning to service.
Traps that cost marks
- Assuming a filter change guarantees air quality.
- Ignoring intake placement.
- Using uncalibrated carbon monoxide or oxygen analyzers.
- Failing to label mixed-gas cylinders.
- Skipping post-event air testing.