Knowledge Review Diver
The primary benefit of using enriched air nitrox is that it exposes you to less nitrogen than diving with air. Advantages include:
- longer allowable bottom time
- reduced need to push near the air no decompression limits
- reduces overall nitrogen load on multiple dives
EANx does not see to affect narcosis while diving, compared with air.
The Primary concern regarding enriched air nitrox and equipment is the high oxygen content.
You may use equipment, other than cylinders, with enriched air up to 40% oxygen, without modification.
The potential hazard of improper enriched air filling procedures is fire or explosion, and incorrect percentage of oxygen in the blend.
Broadly accepted enriched air nitrox cylinder markers include:
- yellow and green band around the tank shoulder, reading "Enriched Air", "Enriched Air Nitrox", or "Nitrox"
- dated visual inspection sticker
- contents sticker or tag
Commom nitrox cylinder markings are not used everywhere. In Europe, EANx cylinders have a white shoulder with a black stripe.
The oxygen partial pressure for the maximum and contingency depth limits are 1.4 ata/bar and 1.6 ata/bar respectively.
The primary hazard of exceeding oxygen partial pressure limits is fatal accident due to convulsing and drowning due to CNS toxicity. Avoid by maintaing good buoyancy control, navigating properly, and paying attention to other factors, such as currents, that may affect your maximum depth.
Signs and symptoms that may precede a CNS convulsions include:
- visual disturbances, including tunnel vision
- ears ringing
- twitching and muscle spasms, especially in the face
- irritability, restlessness, euphoria, or anxiety
Signs and symptoms do not always precede a convulsion.
To use an EANx compatible dive computer to remain within accepted oxygen exposure limits:
- set your maximum oxygen partial pressure to 1.4
- set your specific dive blend
- activate scroll mode that show your no stop limits
If you accidentally exceed the oxygen limit of you computer, ascend immediately but slowly, make a safety stop and end the dive.
You must personally verify the oxygen analysis of an enriched air cylinder always. Use an oxygen analyzer.
If you computer fails during a dive, immediately ascend, make a safety stop at 15 feet for 3 minutes or longer, and end the dive.
If a diver convulses underwater then hold their regulator in place so that it doesn't fall out, but do not waste time putting it back if it has. Establish buoyancy control, and wait until they have stopped convulsing. Immediately resurface at a safe rate, establish buoyancy and check for breathing. Call for assistance and begin rescue breaths if necessary. Get diver out of water as quickly as possible.
If a diver is suspected of having decompression illness after an enriched air dive then monitor their vitals and administer emergency oxygen. If none is available then have them breath enriched air itself. Provide first aid if necessary. Call EMS immediately.