No fly time off gassing rate

[Clammy]

I will be diving this weekend and originally I was going to dive both saturday AND sunday to watch my friends get certified. However, this week I found out I need to fly out of state for work. I scheduled the latest possibly flight I could to get me to the other office in time, which is around midnight on sunday night (technically monday). I can still pull off some shallow morning dives, but would I be able to do a shallow afternoon dive and be okay if I had 8-9 hours to off-gas before my flight. I am wondering what the actual rate of off-gassing is.

Is there some sort of table to figure out a more accurate no fly time rather than the standard 12 or 18 hours?

 

[boulderjohn]

Not really. There are a number of other resources available, but none that I know will give you less time for flying than the the DAN-based policy you cite. Most others will require more time than that.

 

[NAM001]

what is the 24 hr based on? i have often wondered the same as the op. a minute in the water and it is 24 no fly. i assume that it is the recomendation for one coming up from full saturation followed by deco. how many half lifes is needed to become ok to fly to the presurized altitude. since 24 hr is for all it has to be something following the worst case dive sched. isnt the o2 and n2 halflives like 1.5 hour max. and after 6 half lifes there is little left. good ? clammy.

 

[TSandM]

There are no resources that will help you figure out a shorter time-to-fly, unless you have a computer that shows nitrogen loading in the various compartments, and decays it.

The time to fly guidelines are very conservative, especially if you're talking about short and shallow dives, as OW cert dives generally are.

 

[mala]

I will be diving this weekend and originally I was going to dive both saturday AND sunday to watch my friends get certified. However, this week I found out I need to fly out of state for work. I scheduled the latest possibly flight I could to get me to the other office in time, which is around midnight on sunday night (technically monday). I can still pull off some shallow morning dives, but would I be able to do a shallow afternoon dive and be okay if I had 8-9 hours to off-gas before my flight. I am wondering what the actual rate of off-gassing is.

Is there some sort of table to figure out a more accurate no fly time rather than the standard 12 or 18 hours?

its not sensible to do the dive and fly.
whats more important?
dive or work.

just remember if you get sick in the air you will inconvenience a lot of others.

if you are wondering what the off-gas rate is then you really have to follow the guidlines.

 

[Clammy]

I believe that much of the safety margin is based on actual occurrences of DCS in people who flew after diving. I would have thought that by now they would have come up with some sort of table and off gassing rate. One no deco dive or less than 1 or 2 hours total in shallow (something like that) is 12 hours and and multi dives is 18 hours and 24 hours where possible is what a lot of organizations say. Of course this is assuming no deco, no weird combination of altitude and sea level diving, etc etc. I'm probably just going to do 1, maybe 2 shallow short (they are students after all) dives on sunday morning on 40% nitrox, giving me 12+ hours. I know 3 divers that have been chambered (minor DCS, mostly precautionary) in the past month, I hope I don't make number 4. And before people freak out about the numbers, I was diving with 50 divers for 6 days so there was bound to be someone that got a little tingly at some point. One person was somewhere else entirely.

 

[boulderjohn]

what is the 24 hr based on? i have often wondered the same as the op. a minute in the water and it is 24 no fly. i assume that it is the recomendation for one coming up from full saturation followed by deco. how many half lifes is needed to become ok to fly to the presurized altitude. since 24 hr is for all it has to be something following the worst case dive sched. isnt the o2 and n2 halflives like 1.5 hour max. and after 6 half lifes there is little left. good ? clammy.

No one mentioned 24 hours anywhere in this thread.

The recommendation DAN made after their initial research was 12 hours for a single dive and 18 hours for multiple dives/multiple days. As TS&M said, it is a pretty conservative rule at that. In this case, the diver would be fairly close to borderline with morning dives, but not all that close to the border with an afternoon dive.

---------- Post added ----------

I believe that much of the safety margin is based on actual occurrences of DCS in people who flew after diving.

The DAN recommendations were created following a fairly extensive study, the details of which can be found on their web site.

 

[mala]

there are guidlines that range from 2 hours to 48 depending on the dives and the flight.

 

[boulderjohn]

there are guidlines that range from 2 hours to 48 depending on the dives and the flight.

Are you referring to the NOAA table? That does give shorter duration guidelines based upon your ending pressure group on the U.S. Navy tables, which I am guessing the OP might not be using. In addition, that table is based on climbing to altitude by means other than an airplane. For airplane travel, it says to wait 48 hours.

If you have another resource, I would be very interested in a specific identification.

 

[Clammy]

Interesting medical study on DANs site.
Divers Alert Network

1% of dcs estimated risk after a 55 min dive at 60 if flying 12 hours later. These are non-confident results though but still interesting.

I was reading somewhere that DAN's recommendations before the their own trials were coming from analyzing recorded actual instances of DCS from flying. After analyzing the instances, they suggested the 12 hour minimum. Obviously, they've also done trials and other experiments.