Altitude diving

[leabre]

Hi, I'm planning to do some diving in St. George but also to visit friends in Cedar City, Utah (1 hr. away).

St. George is about 2,800 ft and Cedar City is about 5,800 ft. (3k ft. difference).

Will there be any issues with my nitrogen obsorbtion if I leave St. George and drive to Utah within 4 hours after the dive?

I know they say to avoid goin 1k, but my house where I live is about 989 ft. altitude and I go home after beach dive every week and haven't noticed any problems.

Would it be more of an issue at 3k difference?

 

[vixtor]

Not with nitrogen absorption, but with nitrogen elimination eventually as you'll not get more nitrogen, but it will come out.

1000 ft (300m) is not really that much in your "home" case, but 3000 ft (1000m) may be. Normally you shouldn't do this, but as with all the deco theory, it is just statistics, you might be the case when nothing happens, or you may be the case with a DCS hit.

 

[Steve50]

Are you diving with a computer? If not, plan your dive as if you are already at 6,000'.

 

[bleeb]

May be a problem; maybe not. The devil is in the details. Depends a lot on depth and dive times.

One source of information you may want to consider is the NOAA Ascent to Altitude table. Make sure you use the NOAA letter groups, which may be different from everyone else's dive tables. (Other NOAA tables available here.) From this, a moderate depth dive (say 60') near NDLs (60 min) can take you close enough to the edge for a 3000' ascent that you may want to start paying attention.

 

[rollerboi]

Where you planning to dive? Sand Hollow's the first place that comes to mind, which is near St. George at 3000 feet. The last time I went with a dive group, I don't think any of us really worried about the nitrogen loading when we drove home to Provo (4550 feet, but higher altitudes on the way).

A lot probably had to do with the dive profiles as well. Everyone dove pretty conservatively, mainly doing the navigation course or the airplane.

You may want to ask this in the Rocky Mountain Oyster regional group (Travel & Dive Clubs > United States > Western United States > Rocky Mountain Oysters).

 

[Scott]

How many dives and how deep you plan on going? It's all in the planning.
Four hours is a nice 'surface interval' before heading to Cedar City considering at 6 hours you would be 'clean'

Here's a link to some altitude tables. Altitude Table
You sould plan your dives as though they were at 6000 ft.

 

[Thalassamania]

Hi, I'm planning to do some diving in St. George but also to visit friends in Cedar City, Utah (1 hr. away).

St. George is about 2,800 ft and Cedar City is about 5,800 ft. (3k ft. difference).

Will there be any issues with my nitrogen obsorbtion if I leave St. George and drive to Utah within 4 hours after the dive?

I know they say to avoid goin 1k, but my house where I live is about 989 ft. altitude and I go home after beach dive every week and haven't noticed any problems.

Would it be more of an issue at 3k difference?

There's about a half a PSI change from sea level to 1,000 feet ... so that's a change of about 3%. From 3,000 to 6,000 is about a 12% change.

If it were me, I'd plan my dives for 6,000 feet to begin with.

 

[rstofer]

But do understand that when you drive from the lower elevation to the higher elevation, you are still off-gassing. People who drive from Sacramento (essentially sea level) to Lake Tahoe at 6225' arrive as a 'P' or 'H' diver depending on who you talk to and which tables they want to discuss.

What you don't do is arrive as a 'clean' diver. See page 10 here: http://www.ohv.parks.ca.gov/pages/21759/files/dtrt2008.pdf

Richard

 

[Rick Inman]

There's about a half a PSI change from sea level to 1,000 feet ... so that's a change of about 3%. From 3,000 to 6,000 is about a 12% change.

Isn't it that the higher the altitude you START at, the less the bubble expansion? You begin with less dense gas at 3000' then at 0', so the move from 3000' to 6000' has less effect than the move from 0' to 3000'.

I'm I thinking about this correct?

 

[Gene_Hobbs]

Altitude diving resources...

Wikipedia Altitude diving - basic explanation and overview with references.

8thelementdiving.com - Nice article and calculator for "Theoretical Ocean Depth"

If it were me, I'd plan my dives for 6,000 feet to begin with.

Me too...