Why do people add a few minutes to their last deco stop?

[dylanfromwinnipeg]

My instructor says he'll often add a few minutes to his last deco stop, and I've seen a few people on these forums mention that they do a similar thing.

It doesn't make a lot of sense to me, when I hear that in my brain I hear "I don't think my deco plan / GFHi is conservative enough so I'm going to add extra deco on top of it". Why not just decrease the GFHi instead of arbitrarily adding a few minutes on the end (Note: I'm not talking about doing the slow ascent from last stop to surface, I'm talking specifically about adding extra time to the last stop before starting the ascent to surface).

 

[inquis]

Better to add time to the surface "stop" (before climbing the ladder/stairs) if looking for additional conservatism. The off-gasing gradient is larger.

ETA: I only "pad" my last stop when my buddy is unable to ascend because of minor differences in profile, etc.

 

[Johnoly]

..I've seen a few people on these forums mention that they do a similar thing.

You need to clarify because it makes a HUGE difference. Are you talking about a single dive per day or multiple drops on the same day? Because when it comes to fast vs slow tissues, Nothing is free, something pays.

 

[rx7diver]

My instructor says he'll often add a few minutes to his last deco stop, and I've seen a few people on these forums mention that they do a similar thing.

It doesn't make a lot of sense to me, when I hear that in my brain I hear "I don't think my deco plan / GFHi is conservative enough so I'm going to add extra deco on top of it". Why not just decrease the GFHi instead of arbitrarily adding a few minutes on the end (Note: I'm not talking about doing the slow ascent from last stop to surface, I'm talking specifically about adding extra time to the last stop before starting the ascent to surface).

Hmmm. If you're using 100% oxygen, then the last deco stop is at 20 fsw, correct? In this case, is there a need to add minutes to the last deco stop? And, moreover, you need to be mindful of your oxygen clock as relates to not only the current dive but to the repetitive dives, too.

If your last deco gas is NOT 100% oxygen, then aren't the slowest tissues still on-gassing N2 when you add minutes to the last deco stop(s)?

rx7diver

 

[broncobowsher]

Often it is just making sure everyone in the party is cleared, not leaving anyone behind.
If everything went right, you should have a little extra deco gas. You know you can safely get out of the water right now with your already baked in conservitism. What is a couple extra minutes going to cost you? For most people the O2 clock isn't even close to an issue. You can get out right now, but do you have to get out right now? Someone is in front of you on the exit ladder, might as well take advantage of it with a little extra O2. End of the dive, don't have to rush it if you don't have to.

 

[L13]

Hmmm. If you're using 100% oxygen, then the last deco stop is at 20 fsw, correct? In this case, is there a need to add minutes to the last deco stop? And, moreover, you need to be mindful of your oxygen clock as relates to not only the current dive but to the repetitive dives, too.

If your last deco gas is NOT 100% oxygen, then aren't the slowest tissues still on-gassing N2 when you add minutes to the last deco stop(s)?

rx7diver

Adding time to your stops is just as effective at reducing your GF's on 100% as it is on any other mix.

Any tissues that are still on-gasing at 20ft have so little N2 in them that it doesn't really matter, but even more so if you are breathing anything richer than air.

 

[Moerae]

My instructor says he'll often add a few minutes to his last deco stop, and I've seen a few people on these forums mention that they do a similar thing.

It doesn't make a lot of sense to me, when I hear that in my brain I hear "I don't think my deco plan / GFHi is conservative enough so I'm going to add extra deco on top of it". Why not just decrease the GFHi instead of arbitrarily adding a few minutes on the end (Note: I'm not talking about doing the slow ascent from last stop to surface, I'm talking specifically about adding extra time to the last stop before starting the ascent to surface).

The answer is that you're right. It doesn't make sense. But human brains are weird and this gives people the warm fuzzies.

Lowing your GF High by 5-10 will only add a few minutes to your last stop or two for the kinds of profiles most people are diving (e.g. <2 hrs of deco).

 

[DiveLikeAMuppet]

I wouldn’t add anything if running a custom table with a team.

I do add few minutes (or soften/slower the ascent on the last few stops) because the deco that I run on my computers is the bare minimum to get me out as soon as possible, in case that I have a problem. I might add minutes if I have been cold on the dive or if I know that getting back on the boat will be challenging due to weather/gear.

I have seen people dive ?/95 and significantly pad their deco for exactly this reason.

Also, sometimes it’s just nice down there, especially on a CCR your loop is settled at the end of the last stop and you might not feel like getting out yet

 

[admikar]

Because we can?
Seriously though, I'd say it depends. If I'm not cold, there is something nice to see, someone is already on the ladder or I just plain fell like it, I'll add few minutes to last stop.
If there is opposite to anything I mentioned above, I have no qualms about getting out as soon as my stop is cleared.

 

[happy-diver]

When doing "tech" days, from commercial rec boats that "don't " permit deco dives
Captains not necessarily up with deco diving would say, whatever deco you're doing
Double it