Where did the 135 foot / 40 meter recreational max depth limit come from?

[100days-a-year]

 

[John C. Ratliff]

I'm going to go out on a limb and say that the term, "recreational limits" wasn't even used until probably the mid-1970s. Up until then, we simply went by the no-decompression limits published by the U.S. Navy in their Diving Manual. My Dacor Dive Tables, from 1971, do not show that there is a "recreational limit." However, my NAUI Dive Tables, dated 1989, do not list a dive beyond 130 feet (39 meters). So I think somewhere between those two dates, some of the U.S.A. dive instruction agencies decided that 130 feet was the "recreational dive limit," and published their information based upon that idea. I'll have to check my NAUI Instructor manuals for further clarification. I also checked two editions of The New Science of Skin and Scuba Diving (1962 and 1968), and found no reference to "recreational dive limits" or terminology close to that. Joe Strykowsky's book, Diving for Fun, 1974 edition, stated,

"NO DECOMPRESSION" LIMITS

The sport diver can avoid decompression sickness easily. Dives requiring decompression stops make diving quite complicated and take much of the fun out of the sport. Planning and preparations are painstaking and require serious attention to detail. Couple all this with the constant risk of running out of air during decompression and it is clear the sport diver should dive within the "no decompression" limits of the standard decompression tables.

The tables Joe listed in his book go down to 150 feet for 5 minutes for no-decompression, and state:

Bottom Time includes the interval from the moment the diver leaves the surface to the moment he starts his ascent, and not just the time at depth.

SeaRat

 

[scubadada]

I was certified by the YMCA in 1970 also. The only tables in use at that time was the US Navy tables. I think PADI was the first agency to have its own table. Not sure when probably late 70’s early 80’s.

1988, could have been late 1987

 

[scubadada]

As many are having fun answering quarantine questions (thank Pedro for the entertainment) I thought I would toss one out:

Where did the 135 foot / 40 meter recreational max depth limit come from?

No multiple choice answers, but a good old fashioned essay answer.

I shall now socially distance while folks answer.

So... @Scared Silly

What is the answer? You could reveal it under a spoiler like @Pedro Burrito does

 

[Edward3c]

My first logbook contans the RNPL/BSAC Air Diving Decompression Table which was in use until the BSAC 88 Tables were issued.

The one big change was the requirement to make a check stop at 6m. Loads of divers found they were diving too light.

 

[Angelo Farina]

My first logbook contans the RNPL/BSAC Air Diving Decompression Table which was in use until the BSAC 88 Tables were issued.

The one big change was the requirement to make a check stop at 6m. Loads of divers found they were diving too light.

View attachment 582986

These tables are quite conservative. After 30 min at 30 meters, they require a stop of 10 minutes at 3 meters.
The US Navy tables I was using until 1990 assume that after 30 min at 30 meters you should do just a stop of 3 min at 3 meters, which in practice equals the the standard safety stop...
In fact that profile was one of my favourite ones, at those times...
Here my old US Navy tables:

The rec limits, at the time, with a 3rd-degrees certification (what is now called "deep", coming after OW and AOW) did allow for the full first page, and the first column of the second page (hence 51m maximum with 30min bottom time).
For such a dive we usually employed a twin-cylinders tank of 10+10 liters at 200 bar, and an additional pony tank (with a third reg) of 4 liters. This is the setup which I and my wife still own:

All this was considered fully recreational at the time...

 

[Wookie]

I remember the chamber tech telling me that "the reason I was bent" was because I was diving a computer instead of the tried and true navy tables. I may have mentioned that it was because I was old and dehydrated, and to take me to 60 feet for the next 6 hours please.

 

[captain]

Back of my 70 YMCA C card. The front says scuba diver, no basic or advanced is mentioned. We were advised to not dive beyond the NDC limits. Both PADI and NAUI reduced NDC limits, example old Navy table was 60 ft/60 min. PADI and NAUI reduced it to 55min. I think the main controlling issue was the common tank size of the day, a single 72. Beyond 130 the dives could be done to the NDC but it was with double 72's. The Navy based their recommendations based their common use of twin 72's or aluminum 90's.

 

[Edward3c]

...
For such a dive we usually employed a twin-cylinders tank of 10+10 liters at 200 bar, and an additional pony tank (with a third reg) of 4 liters. This is the setup which I and my wife still own

You have the, then, 'new' high pressure cylinders, we were on 160 bar 12Lt.

 

[Must_dash]

My first logbook contans the RNPL/BSAC Air Diving Decompression Table which was in use until the BSAC 88 Tables were issued.

The one big change was the requirement to make a check stop at 6m. Loads of divers found they were diving too light.

View attachment 582986

What year is that from?