Keep your cylinder in service
A pressure vessel is only as safe as its last inspection. Rinse it, store it right, and keep it within test — and it stays fillable, legal and safe for years.
After every dive
Most cylinder problems start on the surface, not underwater. These three habits prevent nearly all of them.
Fresh water, every time
Rinse the cylinder and valve after salt water, paying attention to the valve area and base. Don’t immerse an open valve with the regulator removed — water enters the seat.
Upright, with pressure
Keep 20–30 bar residual so moisture and contaminants can’t get in. Store upright. Never leave a fully pressurised cylinder in a hot car or direct sun.
Fit the dust cap
Whenever the regulator is off, fit the valve dust cap to keep the bore and O-ring clean and dry.
The care kit
The boot and the valve
Two spots do most of the quiet damage. Salt water trapped under a rubber boot accelerates external corrosion — remove the boot periodically to inspect and dry the base. And the valve’s bore O-ring is your primary gas seal — check it often.
- Inspect the DIN bore O-ring before each use; replace if cracked, flat or deformed
- Lubricate O-rings with silicone grease only — never petroleum-based
- Hand-tight plus a half turn on the DIN insert; over-torque damages threads
- Service the valve annually — burst disc and seat are a technician’s job
Testing & intervals
A cylinder with an expired test date can’t be filled at a commercial station. Know your dates — they’re stamped on the shoulder.
| Check | Interval (typical, EU) | Who |
|---|---|---|
| Visual inspection | Annual (per local rule) | Qualified inspector |
| Hydrostatic test (EN 1964) | Every 5 years | Testing body |
| Valve service | Annual / as recommended | Trained technician |
| O-ring check | Before each use | You |
Intervals vary by country and inspection body — confirm what applies in your region with your dive shop or fill station.
Nitrox needs more than a green band
For EAN above 21%, a cylinder must be oxygen-clean inside — free of hydrocarbon contamination — and fitted with an oxygen-rated, oxygen-clean valve. It carries the nitrox markings: the green-and-yellow band and the EAN content label. Most fill stations want a valid oxygen-cleaning certificate before they’ll fill nitrox.