I’ve been SCUBA diving since I was 13. (Somewhere there is a picture of me in a double hose rig with an old 38 cu. ft. tank.) I have enjoyed it all but a very few times. But working around a boat hull with a tank and buoyancy compensator isn’t much fun — don’t bang the hull, don’t snag the BC, don’t get bottom paint on the gear.
So a few years ago, I bought what could be called hookah gear. Basically, it was a hose that allowed me to leave my tank on the boat or in the dinghy while I swam unencumbered as deeply as 60 feet (not that deep was the objective). The limitation was tank capacity. Cleaning a boat bottom can really burn through the air supply,* and I really don’t want to be hauling two 80 cuft tanks around just to make sure one is full.
So, I decided to add an air compressor to the boat. I have friends who use them, and just about every commercial boat diver I have encountered uses them. With our solar panels, running one off the inverter is no problem (neither is running the genset later to make up a deficit on a cloudy day). Pressure output and reserve tank capacity are issues, but the smallest of the “pancake” compressors out there is adequate for diving to the depth of the keel — really all I want. Diving deeper on an anchor would be nice, but now we are talking higher pressure and larger reserve, and space is at a premium. I looked at commercial hookah systems and the prices are outrageous for something I might use twice a year. Actually at ~$1000 – $5000. they are just outrageous, period…
So, for ~$40, I bought an oilless compressor (a widely used one for boat maintenance hookah) planning to add a NIOSH Grade-D (see below) breathing air filter to the output side using inline couplings.
Such filtration for a single line 24 CFM system was available for ~$75 just a few years ago. That number is now between $400-800. Why? A principal material used in these filters was declared carcinogenic. It isn’t, if it’s is properly processed and packaged, but the government… The higher price tag is because Grade-D air must now be delivered via a much more complex (and very retro) filtration system — just the replacement cartridges cost as much as the entire filters used to. It doesn’t help that most of these filters support multiple lines and have bells and whistles that aren’t necessary in a fresh air supplied hookah system using electric power. So now I know why so many of the commercial units have no downstream filtration at all or claim Grade-D performance using components that can’t meet that standard.
Why does it matter? Lungs are hard to replace and once degraded they stay that way. I was part of Texas A&M’s Hyperbaric Physiology program as a student and a lab rat (in the parlance of the time a lab rat was an experimental subject or a student who worked in a lab — I qualified on both counts). Dr. Bill Fife led the program, and I learned pretty much all there was to know in those days. It was a world of lots of experimental and anecdotal data and not a lot of underlying science yet. But many of the old surface-supplied divers of the world suffered through their post diving years with either the effects of overstaying their underwater welcome (decompression sickness) or breathing bad air. After a few autopsy photos of such diver’s lungs, I developed a real fondness for clean air. NIOSH Grade-D is a high standard. C and above are medical grade and higher. The standard is described in ANSI/Compressed Gas Association Commodity Specification for Air, G-7.1-1989.
So setting up the hookah I wanted became a case of go big (bucks, weight, volume) or go home — to properly filtered, tank supplied air.
I’m looking at where to put the tank.
*Resting respiration at the surface is 5-8 liters per minute. This can burn through a tank in about four hours at the surface. When work is being performed at the surface (scrubbing and position maintenance) this can drop to 80 minutes. When depth is considered (5.5 foot draft) a tank will be good for about 70 minutes. If one is in good condition this can be quite a bit longer ~120 minutes. In any case one bottom cleaning is going to require a tank fill