Current state of the Union on heated undies?

[DiveClimbRide]

Please do your research on this. You want the heat on as low as possible in case of a failure until you are ready for ascent. If you have a heat failure and you've had it on so you are nice and toasty in the beginning you're going to bend yourself like a pretzel. You are increasing the rate of inert gas uptake by being warm at the beginning, and if it fails, you are slowing the rate on the way out. The algorithms are based on the assumption that the rates are not changed by any thermal factors, only pressure changes so they can't factor in your temperature. If you take it in faster and the vest fails, you really need to drop your GF-Hi way down to make sure you get rid of all the gas. What @michael-fisch experienced is getting too hot too late and his body trying to dump it all out too fast which is why it's important that you turn it on/up as you are getting ready to leave the bottom. On a wreck that would be on your way back to the ascent line, on a cave it's a little easier to sort out. If you leave the battery on deco if you're in a cave, then it's important to ease into it and not just slam the heat on.

what's the reasoning for being warmer = higher inert gas uptake? Just from a purely chemistry point of view, gases are much more soluble in cold water than in warm water. I would think you want to be warm to slow your initial uptake of gas. While of course it is more complex, see this chart for nitrogen solubility in water as a function of temperature:

View attachment 647826

Coming up, it's much more complex. If you go from cold > hot, you're tissues lose their ability to hold gas, and thus are going to start off-gassing faster. Assuming your tissues don't become supersaturated, that's probably a good thing, as you'll get the gases out sooner. If you lose your heated suits, it might take longer than expected to achieve complete off-gassing.

It seems most reasonable that you want to be warm, and keep yourself warm for the whole dive. That would keep your tissues in a state where they can absorb the least amount of gas, and off-gas at the quickest rate.

I'm not a tech diver (just a chemistry professor), so maybe someone can find a whole in my reasoning, but I think the topic is interesting.

Watch the two videos in the post quoted. I believe it has to do with circulation when the body is hot and cold.

 

[Bobby]

In my blog about out G6 heat controller there are links to Dr. Pollock's peer reviewed work on the subject of heat and DCS.

 

[drk5036]

Watch the two videos in the post quoted. I believe it has to do with circulation when the body is hot and cold.

...what, you actually expected me to watch the videos?

OK, I did watch the first one now, and the second part of it that wasn't linked. Pretty interesting, and the data from the paper presented clearly backs up what tbone was saying. I'm still interested in WHY though, which wasn't clearly explained. I think you must be correct, a change in circulation. Based on that data, I think it makes sense that using heat in the second half of the dive seems reasonable, but you would want to be careful about the temperature. Assuming it is mild heat, less than a hot shower for instance, I think it would have to help off-gassing. But if you go with what the good doc in the video says, you should probably better off just letting yourself remain cold. It'll be uncomfortable, but won't kill you.

 

[barth]

What kind of problems?

I am asking because that is not my experience at all. Me and my boyfriend both use a heated vest and gloves. Never had any issues so far. Last weekend the inside of my drysuit got pretty wet because of a problem with my drysuit inflator and still the heating kept on working fine.

Other divers I know who use Santi (vests and gloves or the undergarments with gloves) never had any problemens. And I do know a few of those people. The water temperatures here in the Netherlands are now around 4 degrees / 39F so a lot of divers use heating, mostly Santi.

Burning marks on the skin and/or burning marks in heating products of Santi.

I don’t know, last summer I did a 3,5 hour dive, max depth >50 meter. I didn’t turn off my heating at the end of the dive at the surface.The result was small burning marks on my skin. Maybe it was my own fault I don’t know, it didn’t happen again.

But this year a lot of people are complaining, much more then in the past.

People are telling me Santi started to using cheaper components. I don’t know if it’s true. But what’s true that a lot of people are complaining about quality of Santi heated products. The burning mark I did see by myself was caused by the connector of a Santi 200 heated undersuit.

(I can sent you names of divers who are complaining by pm.)

I know a lot of people who are using Santi heated products including myself.

 

[rduquesnoy]

Burning marks on the skin and/or burning marks in heating products of Santi.

I don’t know, last summer I did a 3,5 hour dive, max depth >50 meter. I didn’t turn off my heating at the end of the dive at the surface.The result was small burning marks on my skin. Maybe it was my own fault I don’t know, it didn’t happen again.

But this year a lot of people are complaining, much more then in the past.

People are telling me Santi started to using cheaper components. I don’t know if it’s true. But what’s true that a lot of people are complaining about quality of Santi heated products. The burning mark I did see by myself was caused by the connector of a Santi 200 heated undersuit.

(I can sent you names of divers who are complaining by pm.)

I know a lot of people who are using Santi heated products including myself.

Strange, but not something that should happen if you ask me. Any response from the seller and / or Santi?

 

[stuartv]

what's the reasoning for being warmer = higher inert gas uptake?

The short, simple answer is that when you are cold your body restricts circulation to your extremities. Less blood flow to an area means less dissolved gas being carried to or from (depending on whether you're on-gassing or off-gassing) that area. Less blood transported through an area means less gas is absorbed or released.

So, being cold when you're on-gassing is okay. You take up less inert gas in your extremities. Being warm when you're off-gassing is (usually) okay, because you are getting inert gas out of your extremities more quickly.

Tangent alert! This is related to why you may notice having to pee not long after you get into cold water. When your body starts restricting blood flow to the extremities, that means it is retaining extra blood in the core. It stores a lot of that in the spleen (IIRC). Your body will then start working to relieve the stress of all that extra fluid in the core by kicking your kidneys (again, IIRC) into overdrive to pull water out and eliminate it. There is a scientific term for this, which I am too lazy to go look up. I'm sure some smart cookie will post it shortly.

Burning marks on the skin and/or burning marks in heating products of Santi.

I don’t know, last summer I did a 3,5 hour dive, max depth >50 meter. I didn’t turn off my heating at the end of the dive at the surface.The result was small burning marks on my skin. Maybe it was my own fault I don’t know, it didn’t happen again.

I have spent many (MANY!) hours wearing/using electrically heated undergarments while riding motorcycles. My experience is that when you are cold, you can easily turn your undies up high enough to get localized burns and not realize it at all - until you start to warm up. Then it can feel like you are just getting burned. I am speaking from direct, personal experience of more than one occasion. I have done many long motorcycle rides (anywhere from 3 to 15 hours with only stopping for fuel) in temperatures less than 40F/3C. And many more of even longer duration, in warmer (but still cold!) temps.

In other words, even though you forgot to turn off your undies at the end of that one dive, I would strongly suspect you already had been burned and just didn't know it.

 

[BFRedrocks]

@BFRedrocks
I thinking of getting the flex 2.0, any chance you could share how much lead you used with BZ400 VS Flex 2.0?

Hey, tough to say only because so far my only diving with the BZ400 heated full suit and gloves was in Antarctica and salt water (for the most part), and my diving with the Flex 2.0 vest has been in my local freshwater lake. I generally had like 30 lbs (14 kg) during the Antarctica dives (water temp about 1 deg C) and I tend to carry about 18 lbs (8.5 kg) during my freshwater lake dives (water temp about 12 deg C). YMMV.

 

[njdiverjoe]

I've got the LightMonkey heated shirt and it's alright -- on a couple of occasions I've been burnt from it, one resulting in a blister and some scarring. I "mostly flooded" my suit once with it and it appeared pretty useless, I think it just doesn't have the power to heat the water. A lot of the guys I dive with use the Trojan heated vest (70 or 75 watts heat vs the LM at 40w) but I haven't tried it myself.

For canisters I've got a LM and a Trojan canister -- the Trojan wins hands down.

 

[ericfine50]

I've got the LightMonkey heated shirt and it's alright -- on a couple of occasions I've been burnt from it, one resulting in a blister and some scarring. I "mostly flooded" my suit once with it and it appeared pretty useless, I think it just doesn't have the power to heat the water. A lot of the guys I dive with use the Trojan heated vest (70 or 75 watts heat vs the LM at 40w) but I haven't tried it myself.

For canisters I've got a LM and a Trojan canister -- the Trojan wins hands down.

what do you like about the Trojan vest and Canister?

 

[njdiverjoe]

what do you like about the Trojan vest and Canister?

Like I said in my post I haven't tried the vest but a lot of guys I dive have them and love them -- it's also much cheaper than the LM heated shirt.

So for full disclosure I've been diving with the guy who started bringing Trojan over from the EU for some time -- I don't receive compensation for reviews, etc.

Anyways -- the things I like about the Trojan canister:

• for the same capacity it's more compact than the LM one.
• it has a power regulator much like the LM Pitkin controller (I put LM and Trojan as tied here)
• where the entire top of the LM canister opens, the Trojan one stays sealed and only has a port opening to plug in the charger
• overall I get the impression the Trojan canister is of much higher build quality

When I bought my canister I picked it up in person and had him change the E/O cord on my LM canister, The inside of LM canister seems very "garage built" while the Trojan appears to be more professional engineered. Trojan seems to be using higher quality parts as well -- for example the LM cable gland is plastic and super cheap, while the Trojan uses a very nice stainless steel cable gland.

My overall impression is that Trojan provides a much higher quality product and at a lower price point too.