Intro cave limits

[KangarooSeatbelt]

What possible purpose is served by having to use singles?

You can FLY on a single tank... they're really fun dives b/c it's so much easier to move than with doubles. It's good for two reasons I can think of off the top of my head:
1) it keeps intro divers within their distance limits. (800' penetration) Doubles are usually new at that point and the MASSIVE amount of air you suddenly have on your back can give you false confidence to just poke your head around that next corner... single tanks are advantages for intro divers b/c it keeps them in check.

2) it's just a nice refreshing way to visit a cave occasionally for full cavers. Obviously just for fun-ish, but still cool.




in response to earlier comments... I checked my log book, and to the junction room (this is from a single tank intro certed dive) my max depth was 89'

 

[H2Andy]

1) it keeps intro divers within their distance limits. (800' penetration)

which agency is this? i dont' think NSS-CDS or NACD have this as a standard

i believe (without triple checking) that both NSS-CDS and NACD limit you
to 1/3 single-tank, no deco penetration (or 1/6ths on doubles)

 

[Spectre]

1) it keeps intro divers within their distance limits. (800' penetration) Doubles are usually new at that point and the MASSIVE amount of air you suddenly have on your back can give you false confidence to just poke your head around that next corner... single tanks are advantages for intro divers b/c it keeps them in check.

What agency has that limitation? I don't recall that with NACD, and I -know- that you can get pretty far back in peacock on 1/6 of doubles or 1/3 of singles. IIRC my first dive down the peanut tunnel was about 1200' with 500 psi.

 

[GDI]

NACD and TDI does not have any such rule stating 800 ft. I don't know where that comes from. It is noted in the instructors standard to limit the dive of the first intro dive to 600 ft but after that hey the distance is there just stay out of deco. From the book itself On The Intro to Cave Class:

PURPOSE:
To develop basic cave diving skills with limited penetrations in the cave environment. This is the second level of the progression to the full cave diver certification. It is a recreational cave diving course. The course develops and establishes minimum skills, knowledge, dive planning abilities, problem solving procedures and the basic abilities necessary to safely cave dive to limited penetrations, using single tanks.

CAVE DIVES:
Intro to Cave diver certification is based on satisfactory performance of ALL skills listed in these standards by ALL students regardless of prior training. Students will complete a minimum of four cave dives for certification and at instructor discretion one open water evaluation dive. Students using double tanks will use 1/6 air rule. If certified at this level students must be informed they can only dive with a single tank.

LIMITS:
A. Penetration/ depth.
Dive one: 600 feet recommended
All succeeding dives: no penetration limit
Depth: 100 ft

B. Air rules - 1/3 air rules may be used for single tank dives. Students using doubles will use the
1/6 air rule
C. Minimum starting visibility thirty (30) feet.
D. Minor restrictions acceptable. (A minor restriction is when divers are prevented from traveling side by side, forces them into single file travel). No major restrictions.
E. It is highly recommended that additional dives be added at this level. The four dives are the minimum.

 

[loosebits]

You can FLY on a single tank... they're really fun dives b/c it's so much easier to move than with doubles. It's good for two reasons I can think of off the top of my head:
1) it keeps intro divers within their distance limits. (800' penetration) Doubles are usually new at that point and the MASSIVE amount of air you suddenly have on your back can give you false confidence to just poke your head around that next corner... single tanks are advantages for intro divers b/c it keeps them in check.

2) it's just a nice refreshing way to visit a cave occasionally for full cavers. Obviously just for fun-ish, but still cool.

Personally, visiting a cave on a single tank is beyond my acceptable level of risk but that's the great thing about diving, you can tune your risk to whatever you are comfortable. What I don't like is artificial limits placed on my c-card that dictate that I have to accept a certain minimum risk just so I'm not tempted to exceed other limits. Besides, the thought of taking apprentice and full cave without some time in doubles in a cave seems a bit too much to handle.

 

[plankspanker]

D. Minor restrictions acceptable. (A minor restriction is when divers are prevented from traveling side by side, forces them into single file travel). No major restrictions.

I thought even minor restrictions were not allowed. What is the difference between a major and a minor restriction? removal of gear required?

Also aren't some of the agencies specifying a CF allowed for penetration? I thought for sure I had seen that somewhere as a reaction to using large single tanks and diving to thirds.


thanks

 

[Spectre]

Also aren't some of the agencies specifying a CF allowed for penetration? I thought for sure I had seen that somewhere as a reaction to using large single tanks and diving to thirds.

I've seen -minimum- psi and volume restrictions to start the dive, but not maximum. 2000 psi minimum, and I don't recall the volume min.

 

[GDI]

I thought even minor restrictions were not allowed. What is the difference between a major and a minor restriction? removal of gear required?

A minor restriction is permitted at the intro level. By deffinition this is where the dive team members are forced into a single file to move past a point in the cave. An example would be to go through the keyhole at Ginnie. A Major restriction is one the causes the team to not just alter their formation of travel but also requires that the team as individuals must bend and twist or possibly remove equipment to pass through. The passage of a major restriction does not permit the team to pass through ootherwise, again from the book:

DEFINITION OF RESTRICTIONS
For training purposes, restrictions are defined as follows:
Minor restriction - An area too small to allow two (2) divers to pass through at the same time,
forcing divers to swim single file.
Major restriction – Forces diver to manipulate body and/or equipment to pass through.
No removal of life support equipment shall be permitted within the overhead environment.

Also aren't some of the agencies specifying a CF allowed for penetration? I thought for sure I had seen that somewhere as a reaction to using large single tanks and diving to thirds.


thanks

To conduct a Intro to cave dive the minimum size cylinder with a dual outlet valve is 72 cu ft. The minimum starting PSI or Cu ft of available gas is 2000 psi or 50 Cu ft of gas.

 

[plankspanker]

Thanks for the info about the restrictions. I will happily refrain from removing my life support equipment for the time being

I will check my book when I get home but I could have sworn I saw a line about 30 cu ft being the max you could use for penetration for an intro dive. Maybe it was just during training.

 

[ianr33]

You can FLY on a single tank... they're really fun dives b/c it's so much easier to move than with doubles.
1) it keeps intro divers within their distance limits. (800' penetration) Doubles are usually new at that point and the MASSIVE amount of air you suddenly have on your back can give you false confidence to just poke your head around that next corner... single tanks are advantages for intro divers b/c it keeps them in check.

So you are saying that intro divers are not to be trusted and need to be protected from themselves? In which case I dont think they should have the certification in the first place.