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October 2009    Download the Entire Issue (PDF) Available to the Public Vol. 24, No. 10   RSS Feed for Undercurrent Issues
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Why Nitrox Costs So Much

and why you never get it free

from the October, 2009 issue of Undercurrent   Subscribe Now

We frequently get complaints from readers about the high price of Nitrox. A typical one comes from Vicki Caldwell (Sacramento, CA), who dived in April with Osprey Divers at Grand Turk and wasn’t impressed with the prices or the tank mixes. “We didn’t feel like we got our money’s worth because none of the tanks were ever full, and Oasis charges a whopping $13 for Nitrox.” Co-owner Dale Barker was a good sport, agreeing to drop the price to $11 for Caldwell’s group even before they arrived, and then not charging them for their first day’s dives when the Nitrox mix was only 29 percent.

While those figures can add $100 or more to a week’s diving, you can count yourself lucky, Vicky. You’d pay $14 at Aqua Dives in Belize’s Ambergris Caye and $15 at Grand Cayman’s Red Sail Sports. According to John Flanders, owner of the Academy of Scuba in Phoenix and co-owner of Geofish Dive Center in Mexico’s Playa Del Carmen, Oasis’ Nitrox fees are in the middle of the range charged by Caribbean dive resorts. “The average Caribbean tank costs $12 to $15. Compressed air is only $5 a tank on average, so at least half of what you’re paying for is the oxygen, not to mention the costs of shipping it, the man-hours for blending it and the mixing equipment. While some resorts offer “free Nitrox,” nothing is free: Nitrox increases an operator’s cost so it will be made up elsewhere.

Dive operations produce Nitrox in one of three ways: partial blending, continuous blending and Nitrox membrane. Partial-pressure blending is the cheapest technique. A dive shop purchases oxygen separately, then adds a specific amount to an empty, clean scuba tank and tops it off with compressed air. Most dive operations, aiming at a 32- to 36-percent mix, blend gas in a large tank and pump it into individual scuba tanks. It’s labor intensive because it takes time to hook up the bottle, get a precise oxygen reading, then top it off with the compressor. Then the tank must typically sit for 24 hours so gas particles can mix properly.

In continuous blending, air and oxygen mix in a highpressure compressor. The mixture flows through an oxygen analyzer to get the desired oxygen percentage and is pumped into a single scuba tank or a larger storage bank. Big resorts with a steady stream of divers, like Bonaire’s Buddy Dive and Captain Don’s, use this method. It saves time, is less dangerous than partial blending, and blends a large volume of Nitrox with more accuracy. But it’s also pricier. Also, it’s not a great option for liveaboards doing multi-day trips in remote places, as they have limited space to store so many cylinders of oxygen for five dives per day.

Many liveaboards use the Nitrox membrane, which produces blends of up to 40% oxygen by removing nitrogen particles from the air instead of adding oxygen to it. Low-pressure air flows into a filter that removes hydrocarbe bons and other contaminants. Then it passes into a membrane canister, where oxygen, more transferable than nitrogen, filters through thousands of hairlike fibers. To get the proper gas ratio, one just adjusts a needle valve to “dial out” the nitrogen. The de-nitrogenated gas is then transferred to a standard compressor for storage in nitrox banks or filled straight into divers’ tanks. “You can run the system all day, and the cost of making it is relatively cheap as it just uses electricity,” says Bob Olson, president of equipment maker Nitrox Technologies. “But the membrane has the highest initial cost. You’re talking at least $15,000 for a good compressor, and its lifespan averages just five years.”

Wayne Hasson, president of the Aggressor Fleet, says his boats use both continuous blending and Nitrox membranes. It cost $20,000 for the membrane filter, another $30,000 for the low-pressure compressors that pump gas into tanks. Then there are upkeep and maintenance costs. “It’s certainly not cheap. That’s why Nitrox is twice the cost of air.”

Another major cost is shipping oxygen from the producer – it’s not manufactured everywhere. “All our boats are in remote areas, so the cost of getting oxygen to them is expensive,” says Hasson. For the Fiji Aggressor, oxygen is produced in Suva, a three-hour overland trip. For the Costa Rica-based Okeanos Aggressor, the closest supplier is in San Jose, three hours away. While the Nitrox membrane can produce enough gas for all guests on board, it’s still labor intensive, Hasson says. “It takes lots of hours to run the compressor and fill the tanks.”

Dive resorts in bigger places like Grand Cayman have an easier time getting oxygen, as it’s needed for bigger customers like hospitals and the utility company, but DiveTech manager Nancy Easterbrook says shipping costs add up. “Grand Cayman does bring in shipments from the U.S. every week, but tack on to the U.S. price shipping to the Florida port, shipping on the ship to Cayman, duty, insurance, local transport, etc. To get to Cayman Brac, the gas needs to have one more shipping charge also. Our landed cost per cubic foot is almost triple the cost Florida dive shops pay.”

Easterbrook says that for DiveTech to produce an 80-cu-fit tank of 32-percent Nitrox, it needs about 16 cu-ft of oxygen, which costs with shipping, etc., $7.84. DiveTech charges $10 a tank (discounted during slow times) on Cayman, one of the lower prices.

Easterbrook adds that DiveTech is the only Cayman dive shop using liquid oxygen, as she has the volume to justify it (they fill 100 Nitrox tanks a day). ”It’s less expensive per cubic foot than using the gas storage banks but we’ve had to make capital investments to do this. We also have the labor cost of producing our own Nitrox from liquid. Nitrox costs us almost double what air does to produce a tank but we keep a low margin on it to encourage its use and maintain our place in a competitive market.”

Hasson says the Aggressor’s charge of $100 a week for unlimited Nitrox is a deal. “If you do 25 dives, $100 is cheap, compared to buying 25 tanks at $5 to $8 – that adds 25 to 100 percent extra to your total bill.”

Still, if you’re a vacation diver, Nitrox may just be unnecessary expense. At most diving resorts where time and depth are religiously controlled, air will do just fine. While Nitrox builds in a safety margin, especially for older divers, if you’re making just two guided dives a day, following your computer and making safety stops, Nitrox is most likely an expensive luxury.

–Vanessa Richardson

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