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February 1999 Vol. 14, No. 2   RSS Feed for Undercurrent Issues
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Spare Air Mystery Ad

from the February, 1999 issue of Undercurrent   Subscribe Now

“My air gauge went from 2500 psi to 0 in less than 30 seconds. I was down at 120 feet . . . I looked down and saw all of my air rushing out of the swivel....”

What’s wrong with this picture? Something certainly doesn’t fit.

When I read this report in Spare Air testimonial #67 in the July, 1998, issue of Skin Diver, it certainly got my attention. Could a high-pressure gauge swivel o-ring failure at 120 feet really result in a drop in air pressure from 2500 psi to zero in less than thirty seconds? I decided this was something I had to see for myself.

So I tried removing a high pressure plug from my regulator (attached to an aluminum 80 with 2500 psi in it), then opened the valve fully. It didn’t empty in less than 30 seconds. In fact, after 20 minutes, it was still only down to 400 psi.

The thing is, all first stages have high pressure orifices that are greatly restricted and have been specifically designed to prevent exactly the kind of rapid air reduction described in the advertisement. Take a look for yourself: remove the high pressure plug or spg gauge hose from your regulator and look into the opening in the first stage. Both the hose and the HP port have openings approximately the size of the tip of a very sharp pin. The restricted orifice on the hose is in the male fitting that screws into the first stage. They’ve been designed this way since at least 1982.

Ah ha, you may be saying: maybe the answer to the mystery was that, with an o-ring to the pressure gauge blown, it was the gauge that went to zero and not the tank. Clever, but not correct, because even when I REMOVED both o-rings from the high-pressure spool (the little tube encased by the hose-gauge connection that has tiny o-rings at both ends, thus allowing the spg to swivel, even when pressurized), the pressure gauge only showed a pressure drop from 2500 to about 2200 psi.

Okay, then how about just flat-out opening up a tank valve on an aluminum 80 with nothing whatsoever attached to it? Nope, it still takes almost two minutes to go from 3000 psi to zero.

So, try as I will, I can’t seem to figure out what special circumstances could have allowed the tank to empty so quickly. In fact, I tried contacting Spare Air to see if they could give me a clue, but they could only say that their ads share “letters we have received from users where the Spare Air was used to save a life. We believe that the person contacting us is doing so in good faith giving the details as it occurred to them.”

Personally, I was glad to have Spare Air bring me back to the idea of dive safety, because I’d been starting to worry that promoting the idea that you can lose all of your air in 30 seconds could be a dangerous thing. An idea like that just might cause a diver to panic and shoot to the surface at the first sign of an air leak.

Still, it seems a little odd and more than a little irresponsible to feature a so-called testimonial in an advertisement without verifying it. Maybe it did happen, but I’d sure like to know how.

— John Q. Trigger

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