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Bad Air
BobHalstead - 4/29/2013 7:06 AM
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Category: Educational
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By Bob Halstead

Have you ever kissed a smoker? Don’t tell my wife but recently I had the opportunity to plant a smacker on a gorgeous lady’s lips – and nearly gagged. It was a shock. I missed a breath, and the gorgeousness turned to sludge. Now I think about it, Dinah was watching and had a smug grin on her face. The smoky breath reminded me of a miserable dive I once made.

Early in my diving career in the late 1960’s I had heard about bad air – but never experienced it. Then a private yacht sailed into port and after sharing a dive with the owners they offered to fill my tank, for free! I accepted, and thought no more about it until my next dive. I can still smell and taste the foul oily air, groan at the wrenching in my guts and march to the thumping headache from that stinking air. I had to abort the dive for fear of vomiting. I emptied the tank and refilled but the remains of that bad fill hung around for several dives.

I became wary of bad air and tested my air fills by taking a few breaths from my regulator before every dive. Several times I have refused to dive because the air was bad. Amazingly I have been vilified because of my refusal to poison myself. “We breathe it!” “ Its fine!” my senseless, ignorant colleagues have proclaimed. “What sort of a bighead are you?”

Well, I am the sort of bighead that chooses not to breathe bad air.

I once made a complete fool of myself with a dive club in Lae PNG. I had been hired to run a certification course for members of the local dive club. At the first pool session I realised that the club’s portable compressor desperately needed a filter change. The air was foul. Against some resistance I insisted the filter be changed and was told to do the job myself the evening before the club cruised to Salamaua for the openwater dives. The light was not very good and when I dismantled the unfamiliar filter, which was a soggy mess of soaked carbon unable to filter anything, I unknowingly, but carelessly, lost the metal plate at one end that holds a felt pad in place.

The next day we had fresh air in the tanks, but the compressor was filling at a slower and slower rate. We eventually discovered that the felt padding was being pushed into the plumbing and blocking the air delivery. The problem got fixed, but I was blamed for mucking around with their compressor. What I do not understand to this day is how they tolerated that terrible air.

Not only does bad air stink and make you gag, it has bad stuff in it that can cause you serious problems diving. And the deeper you go, the more toxic the bad air becomes.

These days I also take great trouble to see how the compressors are set up in any operation that I dive with. Most compressors are air cooled. They have a fan that ventilates the compressor. This fan needs space to work efficiently. When I see a compressor installed right against the hull of a boat, or wall of a dive shop, I know the compressor cannot work efficiently. If the compressor gets hot it will burn oil. Synthetic oils help but do not solve the problem. The filters will have a short life, and the service life of the compressor is reduced. But I have seen this many times. Sorry guys, but it is wrong!

Many of the problems come from small portable compressors with a very short filter life – say 8 hours. That may be just 15 – 20 tank fills. Then the filter becomes useless and you are filling bad air. Compressor filters like this may need changing every day. Commercial compressors with big external driers and filters set in cool air (outside the engine room) work much better and may go one month or more before change is necessary. But they all need changing eventually.

It is essential that the air intake is in a position clear of any exhausts and able to suck in clean cool fresh air. I have had to stop pumping tanks on occasion because we were close to shore and smoke from village fires was blowing right over our intake.

Here is my advice. Test your air before diving and if you smell or taste any bad stuff refuse to dive and demand money back or a refill. And do not kiss people who smoke.

January 2006