Ascent Pressure

[mccabejc]

I realize it depends on a bunch of stuff, but I'm curious at what air pressure do you typically decide to ascend? Assuming you're going to do a 3min safety stop.

 

[sharpenu]

Depends on conditions. I try to surface with a reserve based on weather and the dive. In ideal conditions on a daytime drift dive at less than 70 feet in warm water on calm seas where I am nowhere near the NDL, I try to reach the surface with a reserve of 300 pounds. Considering that I dive HP120's, this means I have about 10 cuFT as a reserve, which allows 5 more minutes at depth with a normal ascent or a deco stop of up to 15 minutes.

As conditions become more hazardous, I extend the reserve in 200 PSI increments to suit conditions.

 

[DI_Guy]

I am a new diver and have never been a "dive leader" ...

At 1,000 PSI I am thinking about the ascent... At 700 PSI, I am getting ready to ascend... At 500 PSI, I am well into my 3 minute safety stop ...

Depending on the nature of the dive, this could all take place sooner... I always follow the dive plan and leave air in reserve.

 

[ShakaZulu]

This should all be part of the dive plan, and is very dependent on the dive conditions/terrain.

 

[sealkie]

You should start your ascent with enough air to get you and your buddy to the surface - if the dive is a deep dive include a 3 min stop in that ascent


so - it depends on you and your buddy - most people leave it too late

 

[Northeastwrecks]

Depends on the dive. At a minimum, I ascend on a precalculated pressure called Rock Bottom, which is the minimum amount of gas that two divers breathing at a SAC of 1.0 will use to ascend from depth at a safe rate while making all required or recommended stops. Regardless of calculated rock bottom, my minimum rock bottom is 500 psi for dives of less than 60 fsw and 700 for dives of more than 60 feet.

That's the minimum. Usually, I allocate more.

I should probably mention that my calculations are based on doulble 104's and either an AL40 or AL80 stage. Calculations, particularly for the minimums, will vary with configuration.

 

[fdog]

Worst case: enough that both my buddy and I can make it back to the surface while working real hard and buddy breathing. AKA "Rock Bottom".

Although most recreational dives tend to be limited by bottom times. This means I typically am begining the ascent with over half an 80 left, in warm water.

So directly answering your question, it varies.

All the best, James

 

[murphdivers286]

Remember the rule of 3rds. 1/3 for ascending and descending; 1/3 for exploration; 1/3 for reserve. Not everyone follows this rule, but I think it should be a general guide line to follow.

 

[cornfed]

Rock Bottom

 

[roakey]

Search for the many threads that deal with "Rock Bottom"

Roak