Using O2 After A Dive Before Driving Over A Mt. Pass

[OE2X]

I have a friend of mine who lives on the east side of the Mts. and comes over to the coast to enjoy his fix of saltwater diving. To get here he has to go over a 4000' Mt. pass. He generally does one dive on the day that he returns home and waits a minimum of four hours before going over the pass.

The other day we were discussing if he could shorten his SI time by breathing 100% and how long he would have breath the O2 before the nitrogen was purged.

So here is a hypothetical dive. 55 minutes with an average depth of 48' and a max of 110', breathing 32% the whole time.

Can anyone tell me if breathing 100% O2 would shorten his SI time before driving over the Mt. pass, by how much time and how much O2 he would have to breath with a SAC of .5?

 

[SDAnderson]

Can anyone tell me if breathing 100% O2 would shorten his SI time before driving over the Mt. pass, by how much time and how much O2 he would have to breath with a SAC of .5?

It's late and I should be in bed, so double check everything...

Breathing 100% on the surface will definitely shorten his surface interval but I doubt it's worth it. Offgassing is a function of time, pressure and mix; respiratory function isn't a significant factor, so his SAC rate is relevant only when determining how much gas is needed for a specific time and depth.

You don't even need a computer to get a rough answer to your question - each 1000 foot jump in altitude is equal to about 1.1 feet of water. Dig out your tables (mine are in the garage and I'm too lazy to go find them) and add 5 feet to the dive depth and then see how long it takes to offgas on the surface to a "safe" pressure group - I'd use a "D" or better (no rationale for this - it's just a number I'm comfortable with) on the PADI tables. Breathing 100% instead of 32% gives you an additional margin of safety or you can reduce your surface interval - think of it as a deco stop at 5'.

Me? I'd take an hour off after the dive, have lunch with my friends and head on home without worrying about it.

 

[Rick Murchison]

Assuming your dive profile doesn't exceed NDL on your computer, with a 110' max depth, 48' average and 55 minute dive, about the worst case would put you in RG "H" on the Navy table, and NOAA recommends a SI of 3:26 before going over a 4000' pass.
Breathing oxygen could definitely shorten this. By how much? Hard to say. But you can bet your bippy you'll be safer with some time on oxygen before going over the pass than just on air, whatever your SI.
S

 

[JeffG]

I have a friend of mine who lives on the east side of the Mts. and comes over to the coast to enjoy his fix of saltwater diving. To get here he has to go over a 4000' Mt. pass. He generally does one dive on the day that he returns home and waits a minimum of four hours before going over the pass.

The other day we were discussing if he could shorten his SI time by breathing 100% and how long he would have breath the O2 before the nitrogen was purged.

So here is a hypothetical dive. 55 minutes with an average depth of 48' and a max of 110', breathing 32% the whole time.

Can anyone tell me if breathing 100% O2 would shorten his SI time before driving over the Mt. pass, by how much time and how much O2 he would have to breath with a SAC of .5?

His SAC has nothing to do with it...and why doesn't he just get in his car and drive.

 

[yakivet]

I have a friend of mine who lives on the east side of the Mts. and comes over to the coast to enjoy his fix of saltwater diving. To get here he has to go over a 4000' Mt. pass.

Which One??

SNOQUALMIE PASS. Elevation: 3022 ft
WHITE PASS. Elevation: 4500ft
STEVENS PASS. Elevation 4,061 feet

On all of these passes, its gonna take atleast 1 hour to hit the summit, probably more, from the time of his departure. And thats with a slow gradual increase in altitude. I agree with the "reefraff", if your friend takes his time putting away his gear, stops for some food, and hangs out a while, it will be close to 4 hours before he hits the top. Far different from jumping on a flight and hitting 4000 ft in the first 10 minutes. Anyway, its just a view from another eastsider. Ken :42:

 

[Diver0001]

I have a friend of mine who lives on the east side of the Mts. and comes over to the coast to enjoy his fix of saltwater diving. To get here he has to go over a 4000' Mt. pass. He generally does one dive on the day that he returns home and waits a minimum of four hours before going over the pass.

The other day we were discussing if he could shorten his SI time by breathing 100% and how long he would have breath the O2 before the nitrogen was purged.

So here is a hypothetical dive. 55 minutes with an average depth of 48' and a max of 110', breathing 32% the whole time.

Can anyone tell me if breathing 100% O2 would shorten his SI time before driving over the Mt. pass, by how much time and how much O2 he would have to breath with a SAC of .5?

You'll find a table in the U.S. Navy diver's handbook (I don't have it on hand) for minimum surface intervals before ascending to altitude. I seem to recall that it has groups on it the same as the Navy tables so to be conservative you'll have to use group Z and go from there. If you're sure you're within the NDL's for the whole dive then you should be able to use the maximum group associated with the maximum depth you reached. But the way you guys do your profiles I'm not sure you can categorically say that you're always inside the NDL's so maybe Z is better.

Obviously breathing O2 would shorten up the surface interval but you should take a peek at your exposure limits. The SAC is irrelevant.

Hope that helps.

R..

 

[Rick Inman]

Which One??

SNOQUALMIE PASS. Elevation: 3022 ft
WHITE PASS. Elevation: 4500ft
STEVENS PASS. Elevation 4,061 feet

On all of these passes, its gonna take atleast 1 hour to hit the summit, probably more, from the time of his departure. And thats with a slow gradual increase in altitude. I agree with the "reefraff", if your friend takes his time putting away his gear, stops for some food, and hangs out a while, it will be close to 4 hours before he hits the top. Far different from jumping on a flight and hitting 4000 ft in the first 10 minutes. Anyway, its just a view from another eastsider. Ken :42:

Well, this is something we were talking about during a long surface swim, and I posted this similar question here.
To address your question, it was SNOQUALMIE PASS, Elevation: 3022 ft. Right after the last dive, we spend about 30 mins swapping lies, then I took a leisurely drive over to Seattle Marine and bought new dry gloves and liners (10.00 vrs. 69.00 at local LDS), stopped at the bottom of the pass for Oysters at Skippers, and then made the drive over. And, right Ken, the pass makes a very gradual clime up to about 2000', the a quick up and down over the summit.
Sounds like the cost/effort of a breathing the O2 would not be worth it, but it might be fun to see if a passing cop would take notice of be driving and breathing off a regulator. ("Really, Officer. It's just oxygen. Wanna' hit?")

 

[yakivet]

It might be fun to see if a passing cop would take notice of be driving and breathing off a regulator. ("Really, Officer. It's just oxygen. Wanna' hit?")

DWO- Driving while oxygenated. :42: Ken

PS: Was looking for that 50th post to slide me past that "junior member" classification. Thanks Rick.

 

[Flamebug818]

it would be cool to have a cop pull over will breathing a reg i recall that u r supposed to wait 24 hrs to be absolutly safe but that seems way to conservative

 

[OE2X]

PS: Was looking for that 50th post to slide me past that "junior member" classification. Thanks Rick.

How's it feel to be regular? Rick you are so helpful.