We use a DNAX membrane for mixes up to 36% and blend for mixes up to 100% O2. Pure O2 up to 3000 psi for those properly certified in advanced nitrox.
Class E 21% (standard compressor air) 50 to 120 cuft $5.00
Class E 22% to 32% 50 to 80 cuft $8
Class E 33% to 36% 50 to 80 cuft $10
Over 80 cuft add $2
Class E 22% to 36% pony (up to 45 cu ft) $5
Custom Blending above 36% $.38/cuft O2 +$6
Rentals alum 80's 32% $13
Rental steel 95's or HP100's $15
What is Class E air? Compressed air is sampled and tested quarterly for purity. Air falls into different levels of purity called Class. Class D is commonly used for SCBA or fire department use under normal ambient pressure. It has up to 1000 ppm carbon dioxide. Class E is suitable for scuba diving with up to 1000 ppm of CO2, but with up to 25 ppm of hydrocarbons. Class J has up to 500 ppm of CO2 and less than .1 ppm hydrocarbons suitable for oxygen applications.
If a tank or regulator was O2 cleaned and O2 compatible, care must be taken to use only Class J air or there is risk of contamination.
DNAX DE-NITROGENATION SYSTEM.
This system uses a membrane osmosis system that removes nitrogen instead of adding oxygen. Because oxygen molecules are smaller than nitrogen molecules, they are more easily passed through a membrane and sent to a compressor. The initial cost may have been higher than a partial pressure mixing system, but we can produce high volumes of nitrox without adding oxygen. Output is EAN from 22% to 36%, Class E nitrox.
It is the Brass Anchor position that O2 cleaning is not required for tanks, valves, and most regulators provided that the oxygen percentage seen by the equipment does not exceed 36%. This decision is based upon the recommendations made by leaders in the scientific and recreational use of EAN (Enriched Air Nitrox). In particular, BASC has consulted with Dick Rutkowski [retired Deputy NOAA Diving Coordinator, past Director of the NOAA Hyperbaric Facility, founder of Hyperbarics International, Inc., founder of IANTD (1985), and co-founder of ANDI (1989)] on our position. Mr. Rutkowski is in agreement and has stated that NOAA guidelines allow scientists diving with EAN mixes less than 40% oxygen to utilize their standard diving gear without modification. Mr. Rutkowski's experience in NOAA and subsequently has involved 10s of thousands of EAN fills and he has stated that no accident has ever occurred using standard diving equipment that is exposed to oxygen levels of 40% or less. Quoting a press release from Mr. Rutkowski: "As for the recreational diving community, as long as the user never uses more than a 40 percent oxygen mixture, he can use his equipment the same as air safely, as it has been done for over 50 years." Mr. Rutkowski cautions that: "Any piece of equipment that handles more than 40 percent oxygen by volume must be cleaned for pure oxygen service."
Because the DNAX system installed at the Brass Anchor is limited to EAN with a maximum oxygen concentration of 40%, no equipment filled by this system will come into contact with oxygen at the percentage which requires oxygen cleaning or special procedures. While most modern regulators can be used with EAN up to 40% with no modifications if they have been serviced regularly, some manufacturers state that they may void warranties if equipment is used for EAN. Check with BASC for your manufacturer's position in regard to EAN.
The dive industry is currently re-evaluating policies on nitrox and equipment used with nitrox. BASC will change it's policies if necessary to align with national industry standards.
WHY USE EAN?
As stated in the PADI Enriched Air Manual, the principal use of EAN is to extend the no decompression limits beyond the normal air no decompression limits. In addition, divers using EAN within the maximum partial pressure of O2 of 1.4 ata may reduce the chances of DCS if they dive using air tables or an air computer. However, practically speaking, the probabilities of DCS while diving within the limits of the PADI Recreational Dive Planner are so small that it is unlikely that safety is improved to any significant degree. In addition, you cannot "go deeper" with EAN as many people think. In fact, the higher O2 mixes limit you to shallower depths because of the possibility of oxygen toxicity effects above a safety limit on pO2 of 1.4 ata. For example, with EAN32 and EAN36 (the two most popular mixes) the depth limits are 111 feet and 95 feet, respectively.
There have been claims of less narcosis, lower air consumption, and a feeling of well being after a dive. However, as the PADI Enriched Air Manual points out, oxygen also has a narcotic effect and the subjective claims of "feeling better" are not yet proven.
The big advantage of EAN is in the 60 foot to 120 foot range where most divers run out of bottom time before they run out of air. At shallower depths bottom times are usually so long that most divers will run out of air or get cold before they run out of bottom time. Since 130 foot is the maximum depth range for recreational divers, exceeding this depth should be left to the technical diving community.
For whatever reason you wish to use EAN, even if its only to fulfill a curiosity or improve your fund of diving knowledge, it is important to receive proper training. BASC offers the PADI Enriched Air Diver specialty at a cost of $175 which includes all materials, EAN tables, and tank rentals.