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November 2015    Download the Entire Issue (PDF) Available to the Public Vol. 41, No. 11   RSS Feed for Undercurrent Issues
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Do Sport Divers Need a Spare Air?

not if they’re paying attention

from the November, 2015 issue of Undercurrent   Subscribe Now

When a sport diver runs out of air, it's mainly because he's not paying attention to his gauge. At a DAN seminar at the recent Diving Equipment & Marketing Association Show (see the previous article), it was clear that in many out-of-air cases, the diver is so focused on another activity, such as spearfishing or photography, that he doesn't check his remaining air.

Of course, no one should run out of air, but some sport divers who worry about such an event carry small pony bottles, such as the Spare Air, a bottle about the size of a child's forearm with a regulator attached, for a backup. It will deliver a few extra breaths, not enough for any sort of unplanned decompression stop, but enough to get you to the surface from maybe 100 feet.

I recently received an email from one of our readers, Daniel Spitzer (Piermont, NY), who was diving in Tobago with Blue Waters Dive'n in February. He wrote, "As I filled my Spare Air from a tank, Wayne Palmer, who runs the dive operation, sauntered over and said, 'We don't use those here, and they're forbidden. They explode, and anyway, divers use them to extend their bottom time dangerously, and we come up here at 600 PSI.'"

Spitzer had emailed Palmer's staff a question about his Spare Air before he arrived, "but they had not told me of this rule! And I won't even begin to describe the hassles involved in bringing the empty thing through TSA security. . . But I left the Spare Air behind on the dock." The dives were to 65 feet and "I would typically return to the boat at 50-plus minutes, with half a fill remaining in my aluminum 80, despite not having my Spare Air available."

Though some divers get added comfort with a Spare Air, we think it just adds bulk and one more potential complication, especially if you're diving with a guide at reasonable depths. While the possibility of the Spare Air exploding underwater is a red herring, the little pony tank may indeed encourage a diver to get dangerously low on air, run out and have to rely on the very limited capacity of the Spare Air to surface.

John Bantin, the former technical editor for Diver magazine, said, "I attempted to make an ascent from 100 feet with it and came to the conclusion that it was 'three breaths from death.'If you have one, I suggest you try using it for an ascent while still able to retrieve a good supply from your main tank. Then you can make a decision as to whether it is worth the hassle of regular testing and carrying it in your travels and underwater."

Bret Gilliam, the founder of Technical Diver International, says, "While it has proven to be a reliable bail-out, it's severely limited in life-support time, maybe five to seven breaths from depths deeper than 60 feet." If he's doing a complicated dive, he says, "I'd prefer more capacity."

Bantin says you're better off to "consider your age, weight, and overall health to figure out the right amount of air you need. If you are a big, unfit, older man, you might consider a bigger tank, or even doubles if you are diving alongside a smaller, more fit young woman, for example."

For divers who indeed want an extra independent breathing source because they're doing something other than a guided Caribbean dive, like tackling the wrecks in Truk, Gilliam suggests a cylinder in the 15- to 18-cubic-foot volume to mount on the right side of the primary tank on your back. "This gets it out of your way, and yet the second stage can be routed under the armpit to a fixed point on your chest where it is easily accessible if needed. A cylinder that size is very light and not cumbersome, but it will provide plenty of air to get up from depths of 150 feet or so with a controlled ascent rate, and even allow extra capacity for an unplanned decompression stop."

The Y-valve is popular among European divers. "It allows you to fit two complete regulators to one tank, avoiding regulator failure problems," says Bantin. "I carry a set of Buddy Twinning Bands and Blocks from AP Diving ( They are very lightweight in the luggage, yet allow you to twin up any locally sourced cylinders. (You need two complete regulators to use two independent tanks in this way.)"

Having a serious equipment problem at the end of a dive is highly unlikely. Says Bantin, "In more than two decades of intensive diving, I never suffered any such regulator failure, although I suppose it could happen. Regulators are mainly designed downstream-style so that they fail in the open position and free flow." Every diver should know how to breathe from a free-flowing regulator, and every diver should be able to get to the surface from 60-foot depths with a controlled emergency swimming ascent.

If you still want to tote a Spare Air with you, verify with the resort or liveaboard that it is not prohibited, hoping that, unlike Spitzer, you get a straight answer.

-- Ben Davison

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