Get trained
This page explains what training agencies, standards bodies and diving medicine bodies publish. It is not a substitute for training and certification from a recognised agency, and it does not replace medical advice.
Requirements, not procedures
This page records what bodies require of nitrox equipment. It does not explain how to mix, blend or analyse gas, how to oxygen-clean anything or how to plan a nitrox dive. Those are taught in a nitrox course and carried out by trained technicians and fill stations.
The European standard
EN 13949:2003, "Respiratory equipment, Open-circuit self-contained diving apparatus for use with compressed Nitrox and oxygen, Requirements, testing, marking", covers open-circuit scuba for nitrox, defined there as gas with more than 22% oxygen, and for oxygen. It adds requirements, exceptions and tests on top of EN 250, the regulator standard described on regulators. The Estonian catalogue lists it valid from 1 May 2003 and links it to the EU personal protective equipment regulation, (EU) 2016/425.
A BSI catalogue summary lists its contents as including oxygen compatibility, oxygen cleanliness, pressure vessels and valves, an oxygen pressure surge test and marking. Its status is reported differently: one vendor lists it simply as current, while BSI's listing shows it as current and under review. We saw both only as search summaries.
Where the oxygen line falls: the bodies disagree
Each body below draws the line at which nitrox equipment needs special treatment in a different place. They are different positions for different purposes. SDI notes that maker specifications and local law take precedence.
| Oxygen content | Who says it | What they say |
|---|---|---|
| Above 22% | EN 13949:2003 | The scope of the European nitrox and oxygen standard. |
| Above 23.5% | DAN (equipment repair workshop page, undated) | Regulatory codes and safety standards treat gas above 23.5% oxygen, especially above 125 psi, as pure oxygen. DAN warns that people wrongly assume only very high concentrations can support combustion. |
| 23.5% or more | Luxfer (cylinder maker) | Any Luxfer scuba cylinder filled with 23.5% oxygen or more must be cleaned for oxygen service as if for pure oxygen. A maker requirement. |
| Above 23.5% | US DOT (PHMSA interpretation letter, 2011, search summary) | Mixtures above 23.5% oxygen should be treated as more likely than air to cause or contribute to combustion. This is a transport ruling, not a diving rule. |
| 25% or more | DAN Alert Diver (Francois Burman, 2022) | Recommends treating equipment that controls breathing gas of 25% oxygen or more at typical cylinder pressures as oxygen-service equipment. |
| Above 40% | SDI (2012) | Cylinders and valves exposed to more than 40% oxygen at pressures above regulator intermediate pressure must be oxygen clean and service rated; SDI recommends it for any cylinder set aside for nitrox. SDI says maker specifications and local law take precedence. |
| Up to 40% | Mares (REBEL manual, maker statement) | For non-European countries only, its regulators may be used with nitrox of no more than 40% oxygen, citing the DAN nitrox convention of November 2000. In Europe the manual treats EN 250 as an air standard. |
| Up to 40% | Navy-derived practice (retailer article, search summary) | Many technical divers and agencies are said to follow a US Navy approach that treats mixes up to 40% in open-circuit regulators like air, while industrial standards are stricter. The same source calls the idea of "nitrox ready" equipment controversial. |
So the published lines run from 22% through 23.5% and 25% to 40%. Which one applies to a given cylinder, valve or regulator is set by its maker, the fill station and the law where it is filled, not by this page.
When oxygen cleaning is required
DAN's Alert Diver (Burman, 2022) makes the point that oxygen cleaning is not a periodic task. DAN says it is required:
- when equipment is first put into oxygen service;
- when components are replaced;
- after servicing, including cylinders after a hydrostatic test;
- when contamination is found or there is doubt; and
- whenever the maker requires it.
DAN says only properly trained, competent technicians should carry out oxygen cleaning, and that no process guarantees completely safe equipment. Its equipment page adds that choosing the right lubricants and seal materials is critical when oxygen-related equipment is serviced.
SDI (2012) says a cylinder keeps its oxygen-service status only while it is exposed solely to oxygen-compatible air or nitrox made from it. If ordinary scuba air gets in, SDI says, the oxygen-clean markings should come off.
Cylinder bands and tags
SDI (2012) describes the industry nitrox band as a wrap about 10 to 13 cm wide around the cylinder, usually yellow with "Enriched Air" or "Nitrox", or both, in green. It notes that some countries legally require other designs.
SDI also says a tag or label must show the exact oxygen fraction and the maximum operating depth. A TDI guide adds the initials of the person who analysed the gas and the date of analysis. How those figures are arrived at is taught in a nitrox course.
Computers and nitrox
PADI lists nitrox compatibility as a standard dive computer feature. Dive-shop listings for PADI's nitrox course include setting a computer for nitrox among the topics. See dive computers.
Nitrox training
Agencies train divers in nitrox use, as a separate course or within an entry-level course, and the ages and details below are each source's statement.
- PADI Enriched Air Diver: PADI's undated course page, seen only in a search summary, gives a minimum age of 12 and says it can be earned as part of the Open Water Diver course, qualifying divers to use enriched air for no-stop recreational diving. An Australian retailer lists 16 instead. Dive-shop listings give Open Water Diver (or Junior) as the prerequisite and list equipment topics such as cylinder standards, decals and analysers.
- SSI Enriched Air Nitrox: SSI lists ISO 11107, the standard for nitrox diver training, among its ISO programmes. SSI's pages, including its 2024 training standards, seen only in search summaries, describe the course as aligned with ISO 11107 and certifying at two levels, EAN32 and EAN40, with a minimum age of 10 and a maximum training depth of 30 m.
- BSAC: BSAC says basic nitrox training is part of its Ocean Diver course.
A nitrox card is about the diver; the equipment rules above are about the kit.
Sources
- Estonian Centre for Standardisation, EN 13949:2003
- BSI Knowledge, EN 13949:2003 (catalogue summary)
- Standards Ireland shop, EN 13949:2003 (search summary)
- PHMSA interpretation letter (2011, search summary)
- DAN, equipment repair workshop
- DAN Alert Diver, oxygen cleaning (Francois Burman, Q3 2022)
- Luxfer cylinders, FAQ (maker)
- Dive retailer article, nitrox ready (retailer statement, search summary)
- SDI, nitrox tank preparation, marking and identification (2012)
- TDI, how to label your nitrox tank
- Mares REBEL regulator manual (maker)
- PADI, Enriched Air Diver course page (search summary)
- Dive-shop listing, PADI Enriched Air Diver course (operator statement, search summary)
- Dive-centre listing, PADI Enriched Air Diver course (operator statement)
- SSI, Enriched Air Nitrox training standard
- SSI, about SSI
- BSAC, Ocean Diver beginner course
- PADI, dive computers