I have to ask: How many had a fire in their dry suit using 50%

[Akimbo]

... Don't doubt it any more it happened in 1965 at EDU which was next to first class diving school I was in first class school shortly after the fire that killed divers. On my duty nights we spent a few hours in the chamber cleaning up the inside of the burned chamber. I was in class 1666. Washington Navy yard. Just reread your post I see where you posted about the fire at EDU, sorry

The main reason I doubted the story was the ignition source. Besides, I never read about it again. I suspect that they were taking some liberties regarding the hydrogen-oxygen fire on deck during the Arne Zetterström experiments in 1945 in order to make a point. Unless the communications electronics were very different than what the USN used, it would be really improbable that sufficient heat could be produced in the hat. I was an electronics tech and spent a lot of time repairing those old vacuum tube comm boxes. Voltage and especially current was pretty low even in any circuit failures I can think of.

For other readers:
Deep sea underwear was wool in the 1930s. Though highly flammable, it was also pretty damp from sweat and usually sea water. The spark from the comms in the hat would have to occur very close a wool watch cap in order to complete the fuel, oxygen, and heat requirement for ignition.

Chambers are a different animal than inside a suit. Especially at EDU before the fire, there were a LOT of electrical components supporting the experimental dives, nobody fully appreciated how critical high PPO2 levels were to fire risk, and the amount of electronics increased many times from what everyone got away with in the past.

Sidebar:
Sealark, I would really enjoy hearing more about your experiences on the "other side of the wall" at EDU when you were at First Class School. By the time I came along 5-6 years later the EDU chambers were barely visible due to all the added gas and electronic systems blocking the view. All I saw were some photos of the complex after the fire. 1965 was REALLY early in the saturation diving R&D timeline.

 

[dreamdive]

OK, so what I have read so far is that there is not really a case in which a diver used his rich gas (50%) with heated undergarments and had a fire.

Just wanted to be sure.

Thanks everybody

 

[Dr Simon Mitchell]

Hi Claudia,

You probably know about these, but I have definitely heard of several verifiable (or at least they were) instances of divers with chemical hot-packs in dry suits getting burned when the hot pack went a bit crazy after addition of 32% in one case and 100% in another. They were not fires as such, but rather a case of the hot pack getting hotter than it was supposed to and the diver not being able to disengage from contact with it quickly (flooding the suit might have been an option!). Peter Lowe posted a link to an article on Divernet about one of these cases but the link is broken and I could not find the article on a quick search. These things can get very hot if put in an environment containing > 21% oxygen. Indeed, they are thought to have been the source of ignition in several hyperbaric chamber fires.

Simon M

 

[dreamdive]

Hi Claudia,

You probably know about these, but I have definitely heard of several verifiable (or at least they were) instances of divers with chemical hot-packs in dry suits getting burned when the hot pack went a bit crazy after addition of 32% in one case and 100% in another. They were not fires as such, but rather a case of the hot pack getting hotter than it was supposed to and the diver not being able to disengage from contact with it quickly (flooding the suit might have been an option!). Peter Lowe posted a link to an article on Divernet about one of these cases but the link is broken and I could not find the article on a quick search. These things can get very hot if put in an environment containing > 21% oxygen. Indeed, they are thought to have been the source of ignition in several hyperbaric chamber fires.

Simon M

Hey Simon,

Thanks a whole bunch for this! I did not even think about hot packs.
I started this thread in response to another thread (by kr2y5) and wanted to make sure that we don't get into trouble using our heaters in an environment >21% when inflating with 50%.

Claudia

 

[Akimbo]

OK, so what I have read so far is that there is not really a case in which a diver used his rich gas (50%) with heated undergarments and had a fire...

Of course EDU (USN Experimental Diving Unit) didn't have a fire for about 38 years of continuous operation either. I think the more prudent take-away from this discussion is it is improbable but "MAY" not be the most prudent course. Unless perhaps you are in Arctic waters, I also wonder if electric heating is the best option for thermal protection on 50/50 bottom gas.

 

[boulderjohn]

I also wonder if electric heating is the best option for thermal protection on 50/50 bottom gas.

I don't think they are using 50/50 for bottom gas. I think the purpose is to avoid using trimx for suit inflation.

 

[David Doolette]

Not exactly an electrical fire, but I know of two case reports of divers receiving severe burns when using chemical warmers inside a dry suit in combination with high-oxygen-fraction inflation gas. 1) Anderson GP. Skin burns as a result of using commercial hand warmers in a dryduit suing nitrox as a breathing gas: case report [abstract]. Undersea Hyper Med 2005;32:244 available at http://archive.rubicon-foundation.org/1655, that on was 32% oxygen at 135 fsw. 2) Curran JN et al. A case of deep burns while diving the Lusitania. J. Plast Reconstr Aesthet Surg 2010;63:e579-81 [ePub]. Available at: http://www.jprasurg.com/article/S1748-6815(09)00866-3/fulltext, that one was ~80% oxygen at 80 msw. The abstract and a summary of the article are reprinted in Diving Hyperb Med 2013:43(2):113.

 

[dreamdive]

Not exactly an electrical fire, but I know of two case reports of divers receiving severe burns when using chemical warmers inside a dry suit in combination with high-oxygen-fraction inflation gas. 1) Anderson GP. Skin burns as a result of using commercial hand warmers in a dryduit suing nitrox as a breathing gas: case report [abstract]. Undersea Hyper Med 2005;32:244 available at http://archive.rubicon-foundation.org/1655, that on was 32% oxygen at 135 fsw. 2) Curran JN et al. A case of deep burns while diving the Lusitania. J. Plast Reconstr Aesthet Surg 2010;63:e579-81 [ePub]. Available at: http://www.jprasurg.com/article/S1748-6815(09)00866-3/fulltext, that one was ~80% oxygen at 80 msw. The abstract and a summary of the article are reprinted in Diving Hyperb Med 2013:43(2):113.

Thank you David!

 

[emmbee]

The incident on the Lusitania is something that comes up every so often around here. I'm not going to discuss the specifics, I wasn't there and it's not my place, but just to inform the discussion:
1) the diver was using a chemical heat pack with a high O2 mix in the suit which malfunctioned after some time at depth.
2) it's not clear whether he flooded his suit or the suit flooded itself, either way the reaction was stopped, but not before inflicting extensive burns.
3) he made it back, including his full deco, through sheer strength of character and the skill and dedication of his buddy and others.

I heard a similar story from an Italian diver in Antwerp in November, only luckily he flooded his suit before any damage was done.

Discussing how likely this is is all well and good, but I think it's important to also consider the predicament one would be in if it did happen. You'd be between two debilitating rocks, a burn that requires immediate medical attention and the cold, and a hard place, your deco, or worse, the cave. I'd sooner have the rebreather pack in.

With that in mind, personally:
- no chemical heaters - ever.
- the heated vest must be designed for diving - probably not much of a difference, but when I read about people diving stuff out of a bike shop, overvolted no less, I shudder.
- the power supply must be disconnectable.
- if the heat is on, it's in < 22% O2.

Cheers,

Matthieu