Comments on: Cheap Scuba Gear – Scuba / Spare Air Question?

By: Mike H

Mike H — Tue, 02 Jun 2009 13:22:03 +0000

Both posters above me answered your question better than I could, but I have one thing to add- and perhaps either of the two posters above me can answer it.

The system you have constructed is lacking one thing that SCUBA gear and the Spare Air system have- a regulator. When you breathe air at depth, your regulator adjusts the pressure of the air you breathe so that it’s comparable to the ambient water pressure. At depth- you need more air to fill your lungs and will exhaust your air supply quicker than on the surface. So your 5 breaths may turn out to be 2 or 3. But I think the regulator is what causes this change- so you might not have to worry about that.

I’m not sure if or how this will affect you. Make sure you find out before you do anything.

Other than that- I second everything both posters above me said. It might seem simple- but there’s danger involved if you don’t know what you’re doing.

A simple snorkeling class would be able to teach you a lot, I bet

Spare Air costs about 300- but can be had on sale for 200. Seems like that would cost about what you’re spending on your system and- the life safety it would offer would be invaluable, in my opinion. And it comes with a refill valve to be filled from a regular SCUBA tank.

I’m not condoning this- but if you’re going to do it you should have as much information as possible.

Be safe.

By: scubabob

scubabob — Sun, 31 May 2009 13:21:50 +0000

A reputable dive shop won’t sell you that Spare Air or Odyssey EAS unless you cough up a C card. They have to look after their own skins. The issue is the fact that you’re attempting to use a compressed gas underwater. That actually requires some training, specifically on how a compressed gas behaves in the human body, how cylinders are filled and storage/handling precautions.
I bet that PVC tank you made has some glued fittings. PVC glue is a carcinogen. You’ll be breathing that in. The air you’re using from that compressor isn’t filtered. A normal compressor used to fill scuba tanks filters the incoming air and the compressor itself is designed such that no hydrocarbons from the piston area are introduced into the tank. I bet that foot pump of yours still uses some form of lubrication. The automobile one has grease in there for sure. Again, you’re breathing the stuff and it’s also a possible fire and explosion risk, but granted, given the tank pressure you’re dealing with, it’s low to the point of non existent but it’s still there and given the right conditions it could happen.
As for the “bends”, that’s a depth over time issue.
I’m not comfortable answering the rest of your question regarding improving your device, because if you actually went ahead and used it and anything happened, believe it or not, I could be held partially responsible. So could anyone answering it. Honestly, for the price of that EAS, you could take a course and rent gear anytime you wanted it. You pool bottom time would be in the hour range, not minutes.

Edit: To answer Mike’s further query on this. Yes, he’s missing the second stage. What he has now is the equivalent example of what we’d normally consider an “end the dive NOW” situation. A free flow or a no flow on demand. There’s no demand valve( second stage reg) which is what makes this set up a brief hazardous experience amongst other pitfalls. This “blow valve” of his after ( what I assume to be) his first stage reg, may just be a simple on off valve or no valve at all, hard to tell in the way he’s worded it. That’s as far as I’ll go on the construction of this rig.

By: goindrinkn

goindrinkn — Fri, 29 May 2009 19:39:31 +0000

A few comments on your post. As far as the spare air goes, technically speaking it will do what you are looking for. You can get a larger scuba tank and refill it many times over (however each time it will hold a little less as the pressure drops) The spare air is highly pressurized, You fill it from your scuba tank to 3000 PSI You could never generate that with a foot pump or a home style compressor. (I believe the one in my garage will generate about 180 psi.)

You do want to be concerned with the air from any device that it not specifically filtered for breathable compressed gas. As different gsases can cause different issues when compressed. And the unit that your breathing from must be cleaned properly.

But ALLLLL that aside, here’s the real important stuff. There are issues with breathing compressed gas under any sort of depth, even 10 feet. While scuba gear is expensive, a trip to the hospital would cost way more. I would recommend at least taking a class to learn how to use it before attempting anything that has to do with compressed gas at depth. The class will at least teach you about how your lungs expand when assending, which could cause serious and life threatning issues. You do not need to own every piece of equipment to be certified, but you do need to be certified to fill tanks at a scuba shop. The spareair idea is good if you understand how to use it and the risks. (those risks are there when ever you breath air under water)

The scuba class would also help you understand the answers to questions like “Like I can’t get the bends in 10 feet of water right?” Because technially you can. However you’d run out of air wayyyy before that became an issue. But more likely you could give yourself an AEG (arterial gas embolism) which could kill you. So you need to know what that is, and how it happens.

Since we are talking about breathing underwater, and doing it wrong could get you seriously hurt, I’d not want to use a home made contraption. There’s a reason that scuba equipment costs a bit, simply it has to work or you can die. So it is made to a pretty high standard. At least go to a scuba shop and talk to them about it.