Good post, but I am not sure that the last line is true. If you read stories about the hard core divers diving on the Doria during the 80s, divers used to regularly do two dives a day, going as deep as 240 ft (on air, and decompressing on air). Not exactly an advert for safe diving practice, but it certainly used to be done.
As your own sig line says: Decompression diving was common, long before the "Tech" agencies were born.!
Thanks for your comment.
Well, that's a matter of what risk one takes.
For no-deco air dives, the occurrence of DCS is around 1/100000.
According to stats from the COMEX commercial diving company, given around 1992 to the French Ministry of Labor, occurrence of DCS (mostly type I, i.e. bends) while using COMEX dive tables for
air bounce dives with deco also on air (which is a different story than deco with Nitrox and O2) was found to be around :
1/10000 for "moderate" deco dives (e.g. 20' at 39 meters/130 feet)
1/1000 for so-called "standard" deco dives (e.g. 20' at 51 meters/170 feet)
1/100 for "severe" deco dives (e.g. 25' at 60 meters/200 feet).
I guess these Doria divers (not more than 2 dives a day, right ?) were certainly in the "severe" case. Their second dive may have been done on the top of the wreck (at around 57 meters/190 feet if I remember well). Or not ("china fever" has led to a lot of harm on that wreck).
Recent stats of the French Navy for its MN90 air dive tables (more aggressive than the COMEX tables) with deco also on air give a risk of DCS = 1/30000 globally, but 1/3000 for the range 45-60 meters/150-200 feet. The population of these statistics consists in uber-fit young Navy divers, while stats of the COMEX describe commercial divers of various age, laboring underwater. COMEX tables don't allow deeper than 51 meters/170 feet for the second (and last) dive of the day.
For some people, 1/100 or even 5/100 seems to be acceptable, for others (including me) it is not. Fairly common surgical operations have this amount of vital risk, though, but often there isn't much choice in their case, alas. I think we may agree on that an important point is to know the risk (and its amount) beforehand.
Ignorance is a killer.
My signature comes from some really gross crap
I read in the Encyclopedia of some well-known agency, about deco diving being "taboo" and coming out only in the nineties, with tech diving. As if diving had been limited to no-deco dives to 39 meters/130 feet maximum, all around the universe, ever since the invention of scuba.
Such a lie really irritated me. Deco tables came with Haldane as early as 1908 ; Cousteau and his buddies were already doing
leisure deco dives in the fourties ; deco dives have been the mainstream amongst European divers since then ; and even in North America there was no shortage of experienced deco divers on a single tank of air, I guess, though they seem to be much wiser now
.
PS1: I edited my previous post to make it more accurate.
PS2: Tortuga68 (see post thereafter), please don't forget that bottom time is as important (and maybe more) than depth for assessing the severity of a dive. Actually, the severity scale used by COMEX was defined as max depth (in meters) x square root of bottom time (in hours). A weeny 5 minutes at 50 meters/165 feet is very different from a severe 30 minutes at that depth.
Also I am writing here about deco on air, not on Nitrox/O2, which is a different story.