question on bad air

[Kevfin]

After seeing the original post, it reminded me of this story. Kind of a long interesting read, but it highlights the trouble that can be caused by bad air. Also the problem with older compressors.

http://members.aol.com/kfyi/Onceuponatime.htm

I like the T-shirt idea. Haven't used it, because so far my air has not come from questionable sources. Don't know how else you'd be able to tell besides using our normal senses.

 

[Tony "D"]

hi,

i never had a case of bad air (but allways check for it). Since I'm not sure what to expect when checking for bad air, I thought I'd ask.

So, what does bad air smell like? What does it taste like? Ayone who havd the experience cares to share?

thanks

To help answer your question. Before you take the cylinder from the shop. Crack the valve open and smell it. It it smells sweet don't use it. Like mentioned earlier, take a white clean cloth, hold it tight over the valve and crack the valve. Most of the time, a smell test will tell you the story. Make sure you get your air or rent cylinders from a reputable retailer. Look for an air test certificate near the air station. A good responsible shop will send the air samples out every quarter to a lab for testing. I know I do..... In Florida, it's a requirement by the state health dept that every facility selling breathing air must have it tested every quarter. Plus you may want to ask them when the last time was they changed or repacked the filters. The best thing is to just look at the shop your dealing with. No matter what precautions you take, there is no 100% proven prevention.

 

[Whatgoesdown]

I've come across bad air on a few occasions. Once, because the filters were put in the compressor in the wrong order! Cuba, just because they hadn't been changed in months. You are usually smelling for oil (but any smell is bad, air doesn't smell) which to me smells a bit like plastic or paint. Don't jet a blast of air up your nose, it won't help, cup your hand over the valve and bleed a little air. Along with the t-shirt, rub your little finger in the valve and see if any residue comes off. If it does, don't use the tank.

 

[Jim Bishop]

I had a tank filled at a LDS, did not check the air before I left the shop. Got into the water and had strong oil taste. The shop had just gotten a new compressor. Good thing I was just using the tank to clean the pool. Needless to say I got out of the pool. I let the shop know about the air and have not been back to that shop.

 

[cummings66]

Did they clean your tank, regs and lines for you? They certainly would owe you that much for getting that residue in your lines and stuff.

 

[PaulChristenson]

CO Cop - Carbon Monoxide Tester

The CO Cop - Carbon Monoxide Tester is the first user friendly carbon monoxide tester for the scuba diver. The CO Cop - Carbon Monoxide Tester comes in 2 different versions - one has a connector that hooks up to a standard BC inflator hose, while the other uses a standard Yoke tank fitting so you can test the tank directly without hooking up your gear first.

While there are only a couple deaths a year from Carbon Monoxide in Scuba Air... some feel that is a few too many... and how many people have gotten sick and not died? The only way to know for sure that your air is safe, is to test it.

Manufacturerd by Lawrence Factor, the industry leader in air filtration and nitrox systems, the CO Cop - Carbon Monoxide Tester uses a replaceable filter that changes color when exposed to Carbon Monoxide. Simply hook up either version - the BC inflator, or the Yoke, and turn on the air. In less than a minute, a prescence of CO will make the yellow filter turn a dark brown to black color. If CO is not present - you can use the same filter over again. Each filter is good for about 20 tests, and replacement filters are only 6 bucks.

Price: $49.95

 

[cummings66]

Uh - yep, it certainly can.

Water happens in three forms - solid (ice), liquid, and vapor. If a tank happens to have any moisture inside, much of it will be in vapor form - hopefully all of it. If

I misspoke, obviously you're correct in the forms liquid can exist in. This is what troubles me, in school I was taught that water has 3 states as you said. The exact state depends on thermal energy. To stay as a gas you need thermal energy, a liquid less, and ice uses even less. So in a cool or room temp tank your water will be liquid, only as it's filled will there be enough thermal energy for it to be a gas, once that tank cools it must by the laws of physics condense back into a liquid because you've removed that excess thermal energy.

As I understand it, the more pressure there is the more thermal energy it takes to form a vapor, so under the pressures in a scuba tank it should not be possible to remain as a vapor once it's in there unless you keep it hot. The moment that tank cools it should return to it's water form.

Now the kicker, relative humidity. That will allow water to evaporate and remain as a vapor, but again it requires a certain temperature to be that way, the higher the temp the more frequently water molecules leave the waters surface as vapor which increases the relative humidity.

What I don't know is this, what temp is needed at 3000 psi to cause the water molecules to leave the surface as a vapor? I suspect it's higher than the temps you store your tanks in.

You can see I side with those that say once you put moisture into the tank you're going to have water in it unless you open it up and dry it out. That's why it's important to use good air sources, once wet always wet until the next VIP.

 

[DandyDon]

Good discussion, Matthew. Yep, any moisture that might find it's way into a tank from a faulty compressor would be under 3,000 psi and therefore more likely to condense. My Mom used to use a pressure cooker; wonder why we don't use those anymore....?

I was taught that draining a tank quickly, therefore greatly lowering the temp of the metal, will encourage the possibility of precipitation. Now I'm going to have to hope that someopne who knows more than me can address this better. :silly: