Diving myths taught for safety?

[AfterDark]

I heard about that.

You should read about it sometime very enlighting.

 

[Kokeldil]

I just briefly scanned the posts, but I don´t think anyone has mentioned this one yet. Diving myth:
> Most of your body warmth gets lost through your head.

 

[Rhone Man]

I just briefly scanned the posts, but I don´t think anyone has mentioned this one yet. Diving myth:
> Most of your body warmth gets lost through your head.

It took me a while to work out that this one was most assuredly bollocks.

 

[CT-Rich]

Heat loss through the head is not really bollocks. your brain consumes about 25% of the oxygen your body uses, it is relatively thin layer of fat protecting it (although some people might seem fat-headed than others...) and unlike your arms and legs the head absolutely needs to maintain body temp. So if your head is exposed, the body will keep blood flowing to it and reduce flow elsewhere. Even though your head is losing the heat, your hands and feet will be the ones that feel cold. If you are diving in 70F water with a good wetsuit, you don't need the hood because that is an easy way to shed extra heat into the water. I know there are a few doctors out there with a more precise understanding of the physiology (please feel to correct me), but the head is an excellent radiator of heat especially in water.

 

[AfterDark]

Heat loss through the head is not really bollocks. your brain consumes about 25% of the oxygen your body uses, it is relatively thin layer of fat protecting it (although some people might seem fat-headed than others...) and unlike your arms and legs the head absolutely needs to maintain body temp. So if your head is exposed, the body will keep blood flowing to it and reduce flow elsewhere. Even though your head is losing the heat, your hands and feet will be the ones that feel cold. If you are diving in 70F water with a good wetsuit, you don't need the hood because that is an easy way to shed extra heat into the water. I know there are a few doctors out there with a more precise understanding of the physiology (please feel to correct me), but the head is an excellent radiator of heat especially in water.

That is just what I do when I use my 7mm FJ wet suit in NC during the month of June go hoodless, it is the "equalizer". WhenI hit 60F on the Papoose my head felt it 1st.

 

[nimoh]

It took me a while to work out that this one was most assuredly bollocks.

I'm guessing you mean to say that you proved this one wrong (Mythbusters style). How did you do it?

 

[H20Flyer]

BTW, the shop with which I used to work regularly takes 4 day trips to Key Largo. They travel on the 1st and 4th day, and they dive on the middle two days. They do 4 dives per day. The do a 2-tank dive in the morning (deepest dive first), and a 2-tank dive in the afternoon (deepest dive first). That means that each day the 3rd dive is deeper than the 2nd. Think about all the operations around the world in which DMs do morning 2-tank dives and afternoon 2-tank dives. They are violating the "rule" every day they do it.

How about waiting 12 hours after single dives or 24 hours after deep/multiple dives? If I am flying back I have not been diving the last afternoon and then taking a late morning/early afternoon flight. I sort of wonder how applicable this rule is to a flying in a pressurized airplane. Sure the aircraft could have an issue and lose pressurization (all the masks dropping) but if that happens you might have bigger problems to worry about than DCS.

So I guess the guys from your shop were taking late evening flights back from FL?

 

[iluvtheocean]

I'm guessing you mean to say that you proved this one wrong (Mythbusters style). How did you do it?

speaking of mythbusters -- they did do an episode about heat loss that debunked it. although if every part is protected (wetsuit/gloves,boots) then it's a factor simply because it's the only part not

 

[boulderjohn]

How about waiting 12 hours after single dives or 24 hours after deep/multiple dives? If I am flying back I have not been diving the last afternoon and then taking a late morning/early afternoon flight. I sort of wonder how applicable this rule is to a flying in a pressurized airplane. Sure the aircraft could have an issue and lose pressurization (all the masks dropping) but if that happens you might have bigger problems to worry about than DCS.

So I guess the guys from your shop were taking late evening flights back from FL?

The accepted rule for flying after multiple multiple dives is 18 hours, not 24. That has been both the PADI and DAN recommendation for a very long time now. If you finish your last dive in the late afternoon, you can fly out the next day in the late morning and still be within that recommendation. Even if you used 24 hours as your cushion, 24 hours after a late afternoon dive would be late afternoon the next day, not late evening.

 

[Mr Carcharodon]

I wonder, just how close are those tables? I mean, if it says bottom time of 20 minutes, and you stayed for 25, 30, 40... really, at what point would you get bent?

Not that I would be stupid enough to be the guinea pig to find out.

To get a feel for this try comparing NDLs for different tables. For example the Navy tables give 70 minutes more time at 40 fsw than the DSAT tables. So if you dive 60 minutes past NDL on your DSAT/PADI table, but stay 10 minutes inside NDL on the Navy table are you being reckless or safe? Or do you realize the gray area is very large.

Differences of 20-30 minutes in remaining NDL time between different computers are pretty common for repetitive dives in the 40-60 fsw range. If it is assumed both models are safe it again appears there is a vast gray area rather than a sharp line between safe and unsafe and yet that is the way it us usually presented.