AN IMPORTANT NOTICE ABOUT NITROX

In recent years, Nitrox has become more and more popular with recreational scuba divers. Unfortunately, this growth, and some recent oxygen related accidents during tank filling, and stage bottle use, mean that nitrox blending, and oxygen clean standards are now drawing the attention of governmental agencies such as OSHA and the manufacturer’s legal liability council, as well as the “CE” or European standards agency.((You may not realize it, but most scuba manufacturers sell more equipment in Europe and European commonwealth related countries than they do in the United States)).

The up side of these discussions for recreational scuba is that nearly all of the equipment manufacturers now say their equipment is “nitrox compatible” for blends up to 40% right out of the box, with no special cleaning, or parts needed. Most small shops do nitrox fills using a method called “partial pressure blending.”  This involves putting pure oxygen into the tank, then topping with air.  It is very effective, and efficient, and relatively cost effective to set up. All tanks and valves, however, must be oxygen compatible and oxygen clean, since the first step involves putting the pure oxygen into your tank.  

The alternative to “partial pressure blending” is membrane systems or constant flow systems.  Membrane systems are frequently found on live-a-boards, and in resorts.  They function by subtracting nitrogen from your gas mix – rather than adding oxygen.  They are very safe, but very  expensive to set up and out of the reach of most local shops.  “Constant flow” systems rely on injecting a constant flow of oxygen into the intake of a compressor.  The downside of this is that it voids most compressor warrantees and it is widely recognized by the Compressed Gas Association that compressing high oxygen mixes over 2400 psi is very dangerous.  Most scuba compressor systems are outputting 4000 psi from their fourth stage, regardless of what the shop storage bottles are actually holding.  (normally 3000 – 3800) Bauer Compressors has at least one report of a 4^th stage fire directly attributable to pumping 40% through a compressor.  

In the past, manufacturers required “nitrox kits” for any use over 21% oxygen. This meant that we could get oxygen compatible parts for almost any regulator or valve.  In theory, we could clean the regulator or valve to oxygen use standards, and “POOF” you had an oxygen compatible regulator for stage bottles, and an oxygen compatible valve for partial pressure filling.

With the “40% is the same as air” rule now in place, manufacturers are no longer shipping oxygen compatible kits, because in their view, they are not necessary for recreational scuba use.  In addition, their legal council is telling them that unless the regulator or valve has been specifically tested for oxygen exposure they are facing a product liability nightmare shipping oxygen compatible parts for conversion in the field. According to TDI, and PADI (Dsat) who, among several other agencies offer O2 Technician certifications, the manufacturer’s statements trump anything taught in the certification course.  For an example, Sherwood Scuba says they will not warrantee any use of their regulators over 40%.  The official Bauer Compressor position – “we do not recommend our compressors be used in any nitrox application.”

In addition, the European Union is in the process of creating a “Nitrox Standard” system where all oxygen compatible valves and regulators have a specific DIN fitting on them so they can not be interchanged with standard fill whips, and regulators.  The thinking is that this will reduce the chance that a non-oxygen compatible fill will take place, or a regulator will be used, and this will reduce the chances of an oxygen fueled fire.

What does this mean to you – the diver just trying to get a Nitrox fill, or a stage bottle regulator?  It means that we are having great difficulty getting the Oxygen compatible parts we need to maintain the O2 clean status of your valve for use in Partial Pressure Blending, and we are having trouble getting parts to convert or clean your standard regulator to stage bottle use.  As tanks come up for cleaning, and regulators come in for annual service, we may not be able to return them to oxygen clean status, and you may not be able to get fills, or safely use your stage regulator.

You may ask if this is all necessary.  Sherwood reports three first stage fires in the North East section of the country within the past two years, and they do not recommend any Nitrox use higher than 40% even with a conversion kit. We are unsure of their policy on shipping valve overhaul kits.  Scuba Pro reports at least one oxygen fueled fire in a first stage in the fall of 05 – AND it happened in a supposedly O2 clean regulator, DURING a dive.  The DIN connector sheared at the regulator body from the heat.

So far, three manufacturers that we are aware of are shipping O2 compatible regulators directly from the factory.  Dive Rite – www.DiveRite.com, Apex – www.Aqualung.com, and ScubaPro, www.ScubaPro.com.  Mares has plans to ship an O2 certified Abyss within the next 6-8 months, but it will have the new European standard DIN connection on it.  We carry the DiveRite, ScubaPro, and Mares regulators.

We will endeavor to stay on top of this situation and keep you updated as best we are able.