What Agencies Teach Air Breaks

[Michael Guerrero]

I've skimmed through my TDI books and didn't see anything about air breaks. My understanding based on the summaries of the studies on them (the ones with hamsters and those with people) were that this was mainly to avoid pulmonary ox tox, for conditions you would encounter mostly in chambers (i.e., hours and hours--like 8+ hours--of oxygen exposure). If I recall, they said that a 4:1 (i.e., 20 minutes of high O2, 5 minutes off) prolonged tolerance to high O2 substantially and avoided the symptoms of pulmonary ox tox.

I've seen some GUE types posting details about air breaks (12 on, 6 off if I recall), and so I assume UTD also teaches these. Does any other agency?

I think 8+ hour deco dives are conducted by a pretty small community, so I wouldn't expect to see others using air breaks unless they picked it up from reading something or from someone who practices these.

What do you guys see? Are people doing air breaks on short decos because the cool kids are, or is their agency telling them they should?

Thanks,

Mike

 

[kensuf]

Breaks are good for more than just pulmonary toxicity. Oxygen is a vasoconstrictor, breaks help reset the lungs and capillaries so you can still offgas inert gases. Breaks also help with managing CNS.

I have seen 12:6, 15:5, 20:5 most commonly. Depending on the length of the o2 portion, I'll do either 15:5 or stay on oxygen up to 20. If I did extreme oxygen hangs, I'd probably do the 12:6 route.

For instance, if I had a 19 minute hang I would just stay on oxygen. If I had a 30 minute hang I would do 15:5. If I ever had 120 minutes or more on oxygen again, I would probably do 12:6.

 

[tbone1004]

I usually do 10:2 or 15:5. Depending on the dive you quite often don't have a choice but to go on an air break because your CNS clock is ticking.
If you do a 90min dive at a PO2 of 1.3 which is say a normal dive at Jackson Blue your CNS clock is pushing 50%, that means you only have 20 minutes left at a PO2 of 1.6 for deco until your CNS clock hits 100%. Unfortunately that means that you might have forced air break to bring your CNS clock back down so you can finish your deco. The Petrel is really nice and gives you your CNS clock so you can have air breaks, so whether the agency teaches air breaks formally or not, quite often you have no choice but to go on an air break and the duration you do that is up to you, the important thing is getting the CNS clock back down below the threshold.

 

[LiteHedded]

I do 12 on 6 off if the O2 time is 30 minutes or more

 

[Pullnglide]

PADI teaches air breaks in the 45/50 deep air courses.

 

[PfcAJ]

Oxygen time of 30mins or more gets 12 on 6 off. Off time counts as deco time. I also switch to backgas at the stop before the next gas switch for the duration of the stop.

I totally ignore the cns clock. It's a poor model and doesn't serve to predict much of anything. People tox below 100% and often don't tox past 100%. The only proven method is low ppo2s on the bottom in the 1.0-1.2 range (avg) and the above gas break strategy.

 

[Michael Guerrero]

OK, so TDI at the AN/DP level does not introduce or mention air breaks.

The US Navy manual says that starting at 30' and 100% O2 take a 5 min air break every 30 min if the deco is longer than 30 min. The 5 min air break does not count toward deco.

So how about the rest of the agencies, other than PADI which apparently calls for air breaks in its deep air course(s).?

Question #2: do the agencies that advocate air breaks give a certain exposure beyond which they are recommended (e.g., if deco longer than XX min then take an air break every YY min for Z min)?

 

[PfcAJ]

The first paragraph I wrote describes gue's approach.

 

[kensuf]

I already mentioned what I do. Here's some specific quotes from various instructor guides for courses I'm allowed to teach through both TDI and NAUI.

NAUI's Technical Decompression Instructor Guide has the following statement (Unit 4: Decompression Strategies, Slide 61):

"Five-minute breaks from oxygen to back-gas must be taken every 20 minutes or less!
- Break does not count as deco time."

NAUI's Extreme Exposure Instructor Guide has a similar statement (slide 67):

"When breathing O2, it is important to take normoxic (back gas if not hypoxic) breaks every 20 minutes. This is a USN guideline. The deco clock only runs when you are breathing the gas for which the schedule was generated."

The TDI Advanced Trimix Instructor Guide has the following statement (slide 36):

"Take air / back gas / leaner deco gas breaks to mitigate toxicity levels"

The TDI Advanced Nitrox Instructor Guide has the following statement (Unit 4, slide 7):

"Take oxygen breaks during decompression stops. Be conservative with oxygen exposure."

And the "DP" portion of the TDI AN/DP program does not cover using gases other than air. That's why they're usually combined.

 

[Redshift]

What is the reason behind the 12-6? Seems very precise and other recommendations use multiples of 5.
Also interesting to see that for some air breaks count the same for deco and go others it doesn't.