Multi Day Diving

[Nick Stephens]

Hi Guys,
I wanna know what peoples opinions are on multi day diving. How many days can you dive in a row and how many dives a day, without obviously getting bent.
If you are diving say 3 dives a day on air, my local chamber recommends that you should then take a day off after 3 days of this on the trot.
What are peoples opinions on this subject?
Nick..

 

[draco]

If I have a week to spend on a beautiful coast, I try to do as many dives as I can.
That means 2 dives a day minimun, all on air.
Never took a day off, but I never dived for more than 14 days in a row....
Listen to your body, if it says no, listen to it!

Dive Safe,
Paolo

 

[Tobagoman]

Christ! I've been messin' up for a while then. I've sometimes done 5 tanks in a day (2 morning, 2 afternoon and a night), with 4 tank days the rest of the days of the trip. As long as I tracked nitrogen accumulation and off-gassing when diving on air I figured I would be okay. After 20 years and more dives than I care to count I guess I have been lucky if what your chamber told you is true.

 

[Gary D.]

Just watch your tables and dive until your ALMOST blue in the face.

For sport your just out there enjoying yourself. For working dives your busting your but day after day sometimes for months at a time.

Depends on the time depth and si's.

Gary D.

 

[DORSETBOY]

hi Nick, I realised recently looking back through my log books that when I did my dmt training I was doing 4-5 dives per day every day for a month. As others have said it's quite reasonable to do that as long as you watch your nitrogen intake and ensure you are conservatve with a view to depth / bottom time / surface intervals. Another option to air is using nitrox, but then you've got to watch your O2 exposure!

 

[Charlie99]

As others have said it's quite reasonable to do that as long as you watch your nitrogen intake and ensure you are conservatve with a view to depth / bottom time / surface intervals.

Several have posted comments similar to that above. My understanding of the effect of multi-day diving differs in one important aspect. Rather than being conservative on depth/bottom time/surface intervals, I try to be conservative on bubble formation. Bubbles have a very long lifetime once formed; much longer than dissolved gas halftimes would predict. Once you have significant bubble formation, even after overnight SIs, subsequent dives can further enlarge the existing bubbles.

By "be conservative on bubble formation" I mean
1) Deep stops, preferably by use of a multi-level dive profile that automatically does the deep stops. For typical 100' NDL diving, "deep stops" are simply inserting a couple of 1 or 2 minute stops at 60' and 30'. Deep stops are just another way doing item 2).
2) Careful attention to "time to ascend". I'm not as worried about any momentary instantaneous ascent rate as with the time spent over any 20 or 30' depth change (or more accurately, over any absolute pressure ratio change that approaches 1.5). Multilevel diving, deep stops, Naui half-depth stops, 15' safety stops ---- they are all good ideas.
3) Pay attention to your body. If you are getting tired or beat, back off on the number of dives, or even take a day off. It doesn't matter whether you have minor bubble formation / subclinical DCS or are just feeling the effects of sun and weather. If your body says slow down, then do it.

While the above comments aren't supported directly by any reports or studies that I've seen, they are based upon my interpretations and extrapolations of a lot of different items. For example, if you look at the Suunto RGBM model, the M-value limits will be reduced for up to 100 hours in resonse to things like fast ascents or short SIs.

Nitrox does help, but my guess at why it helps is simply that if you have a lower N2 load, then you can often get away with ascent profiles that would cause bubble formation after doing the same dive on air.

Obviously, a lot of the above is more opinion than hard fact, but for me it has worked well.

Charlie Allen

 

[MikeFerrara]

Good post Charlie

The fact is and it's mentioned in some OW course texts even is that the more dives you do over more days the further you get into non-tested uses of the tables.

Also keep in mind that a fair percentage of the divers who get bent aren't diving extreme profiles but rather multiple days of multiple recreational dives.

 

[eponym]

Charlie hazarded:
Nitrox does help, but my guess at why it helps is simply that if you have a lower N2 load, then you can often get away with ascent profiles that would cause bubble formation after doing the same dive on air.

I do wish I were facing the "how much should I dive" dilemma right now. It's going to be over 100F this week in our little Southern Oregon valley and I'm stuck on dry land tending to a post-operative patient.

But as a follow-up to the quote above, I think it's useftul to remember that bubbles of inert gas (nitrogen in this case) take time to dissipate because, unlike oxygen, they're not used (re-absorbed and combined chemically) by living tissue. So repetitive diving certainly can, depending on depths, ascent rates, exertions levels (in and out of water), surface intervals, etc., put you at greater risk for bend symptoms. Diving Nitrox (once you're certified for it) on the standard air tables is a great way to give yourself an extra margin of safety.

I'd drone on but the diving medicine forums are I think a good place to find more info. Dive safe!

-Bryan

Never be afraid to say hello .

 

[Nick Stephens]

Cheers Guys for your thoughts so far.
Lets get a little technical now.
What about if you do a deep dive, say 40m and go into deco. Do a deco stop as required. How would you then dive the rest of the day, next day etc.?

 

[miketsp]

Cheers Guys for your thoughts so far.
Lets get a little technical now.
What about if you do a deep dive, say 40m and go into deco. Do a deco stop as required. How would you then dive the rest of the day, next day etc.?

Try to avoid sequential deep dives. If you can't avoid them always do your final ascent of the day as slow as possible on the last 15m. Use as much as possible of your remaining air.

Normally when I'm doing more than a week of intense diving there are also a lot of shallow night dives which act as prolonged stops.

Also if you can fit in some nitrox dives that should help.