Soggy
Contributor
Could someone treat the dive as an altitude dive and plan accordingly?
Can I visit 5000' mountains after diving?
- Thread starter jpdonvito
- Start date
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It seems to me that they could.
Best regards.
DocVikingo
Best regards.
DocVikingo
Well, yes and no. This is kinda what we do here in Colorado where we're almost always faced with a pass to go over after diving. Well do the dive as if its at the pass altitude than burn a bunch of time before we head away from the site.
Problem is, your tissues are not at equilibrium for the altitude that youre calculating the dive for. In other words, if you went to 5k feet and stayed there for 24 hours youre going to outgas for 24 hours until the N2 in your body is at equilibrium with the PP of N2 in the atmosphere.
Calculating your dive as a 5k dive while at sea level will not take into account the extra N2 you have in your tissues at sea level that wouldnt be there at 5k feet.
What you might want to do is calculate your pressure group as if you just drove to 5k feet (2 pressure groups per 1k feet, or 10 pressure groups, or an J diver on the Navy tables) and do your dive as if youre going into the water as a J diver AND apply altitude correction to the dive itself.
What do we *really* do here in Colorado? First we dive rich Nitrox mixes. Than we make an educated guess when its OK to head up the pass. So far our guesses have worked.
Roak
BRW
Contributor
Check out "Diving Above Sea Level" (DASL) from Best Publishing. No need for guesses nor ad hoc rules of thumb. Procedures therein have been the bases for altitude diving for 25 yrs. And, of course, they are bases for computer calculations at altitude and well known Table mods (which apparently some haven't seen). Said procedures were also commended to the USN Fleet for altitude operations by Ed Flynn (Capt, USN). NOAA procedures are close.
DASL also catalogs altitude mods to buoyancy, gauges, consumption rate, ambient pressure, etc, in addition to deco and table changes.
For instance, if you use coventional USN-type Tables, you need only wait until you drop into the H group before ascending to 5,000 ft. If you come from sea level to 5,000 ft, you should consider yourself in a D group at the start of the dive. This is old hat and is covered (should be) in any basic scuba class taught above 2,000 ft elevation. If you didn't get it, maybe complain to your Agency for the info. It is "need-to-know".
If you use newer Tables, like NAUI RGBM (dual phase) Tables, check out the rules (tested) attached. These Tables are more correct on basic principles, although differences are small (compared to USN-type Tables) for recreational diving. The FAD rules and ascend-to-altitude
rules are close to the above. Big differences occur for deep, mixed gas, deco, and sat diving however.
Hope you altitude divers get info in your training courses.
Cheers,
DASL also catalogs altitude mods to buoyancy, gauges, consumption rate, ambient pressure, etc, in addition to deco and table changes.
For instance, if you use coventional USN-type Tables, you need only wait until you drop into the H group before ascending to 5,000 ft. If you come from sea level to 5,000 ft, you should consider yourself in a D group at the start of the dive. This is old hat and is covered (should be) in any basic scuba class taught above 2,000 ft elevation. If you didn't get it, maybe complain to your Agency for the info. It is "need-to-know".
If you use newer Tables, like NAUI RGBM (dual phase) Tables, check out the rules (tested) attached. These Tables are more correct on basic principles, although differences are small (compared to USN-type Tables) for recreational diving. The FAD rules and ascend-to-altitude
rules are close to the above. Big differences occur for deep, mixed gas, deco, and sat diving however.
Hope you altitude divers get info in your training courses.
Cheers,
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