Use of Heat Packs inside Drysuits - DON'T!! [Archive]

turnerjd

24-08-2015, 08:56 AM

There was also a guy that got pretty bad burns on a dive to the Lucitania (90m) a few years ago. The pack didnt burst but seemingly the higher ppo2 inside his suit caused a much stronger chemical reaction than normal

That's what any scientist will tell you..... it's not the fO2 that is important for such a chemical reaction, but the ppO2. ppO2, as everybody learns is the equivalent of concentration.

As such, chemical heat packs are a really dumb idea under a drysuit.

Jon

notdeadyet

24-08-2015, 09:33 AM

That's what any scientist will tell you..... it's not the fO2 that is important for such a chemical reaction, but the ppO2. ppO2, as everybody learns is the equivalent of concentration.

As such, chemical heat packs are a really dumb idea under a drysuit.

Jon
Wasn't the guy on the Lusi using a charcoal pack or am I thinking of a different case?

I assumed the heat packs in the OP were the saline gel packs. Surely ppo2 makes no difference to these as they arent consuming oxygen.

turnerjd

24-08-2015, 09:56 AM

OK, - general scientific post so that people can understand what heat packs really are - from the scientific point of view, there are two principal types of heatpack. I know that one is dangerous for diving, and I suspect that the other is too.

The sodium acetate / stainless steel disk - This is based on supercooling - These are identifiable by the metal disk that is in them, they are in a watertight plastic pack, and are re-utilisable simply by heating them up. Basically sodium acetate is more than happy to exist as a liquid at a temperature much lower than its freezing point. Then, when you "click" the metal disk there is a minor disturbance created, that provides the initiation point for crystallisation of the sodium acetate. One the process has been initiated, the rest of the liquid then rushes to solidify as well. As crystallisation releases energy, the temperature of the solidifying liquid can jump up to around 55 Deg C in ideal conditions - but many products are designed to go more slowly, releasing the same amount of heat over a longer time and not getting so hot. They don't consume O2, but I suspect the pressure would have an effect on the speed at which the temperature is reached, and how the heat is dissipated (ie they get hotter faster and are more likely to hit the maximum temperature, rather than more slowly, and not hitting max temperature) and how they crystallise - biologists and chemists regularly play with pressure when we are trying to crystallise molecules e.g. to get x-ray structures afterwards. - so I suspect that this would be dangerous in a drysuit.

The second type is the pouch that contains powder. These are stored in an airtight bag, and are activated when you take them out and shake them. They basically contain charcoal and finely divided iron particles. When air gets in, highly reactive ground-up iron reacts with the oxygen in the air exothermically to produce iron(III) oxide (rust) - this we know is dangerous under a drysuit because of increased ppO2.

HTH

Jon

PlymouthD

24-08-2015, 09:57 AM

There are a few different types of handwarmers. The most common one, which you regularly see flogged in Lidl, is the liquid-filled plastic pouch with the metal disc inside which you 'snap' to activate. As far as I'm aware, these ones are safe. It's just a crystalisation process which gives off the heat, reaching a maximum temp of 130 fahrenheit. There's no chemical reaction going on, and the liquid is non-toxic, so no issue if it ruptures inside your suit. If anyone knows any reason why these ones aren't safe - let me know as I occasionally use them in my drysuit on long boat-rides home when it's really cold. I've even punctured one (not in my drysuit) and the liquid was no more troublesome than water. (Edit due to simultaneous post with John's above. Re: pressure affecting the temperature these things get to: when I first bought a few of these things, I tried them during dives inside my suit, close to my skin. The dives were probably around 30m and I don't recall even noticing their presence - I may or may not have benefited from greater background warmth within the suit. So if they are affected by pressure, my experience has been that the effect is very slight.)

I'm assuming the one involved in this news story is the type which works on a chemical reaction which is triggered by exposure to air. In which case, high PPO2 may be an issue.

And then there are the ones which include smouldering charcoal, which are obviously a bad idea inside drysuits. It was one of these that was involved in the horrific accident where a family were incinerated in a recompression chamber during oxygen therapy.

Logun

24-08-2015, 10:34 AM

There are a few different types of handwarmers. The most common one, which you regularly see flogged in Lidl, is the liquid-filled plastic pouch with the metal disc inside which you 'snap' to activate. As far as I'm aware, these ones are safe. It's just a crystalisation process which gives off the heat, reaching a maximum temp of 130 fahrenheit. There's no chemical reaction going on, and the liquid is non-toxic, so no issue if it ruptures inside your suit. If anyone knows any reason why these ones aren't safe - let me know as I occasionally use them in my drysuit on long boat-rides home when it's really cold. I've even punctured one (not in my drysuit) and the liquid was no more troublesome than water.

The gel with a disk in type aren't really safe for diving either. I have heard a horror story of someone having a few in his drysuit then setting them off on deco. on one particular dive one of them burst, leaving him with pretty nasty burns. it may be that there are several types with some more dangerous than others, but I wouldn't want to risk it. I cant see it being a problem on the boat on the way back though, its a lot quicker to get it off then than if youre at 6m with a shit load of deco left.

hippytyre

24-08-2015, 11:10 AM

I don't think he'll be doing it again anyway. I wonder if flooding his suit might have helped?

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turnerjd

24-08-2015, 11:13 AM

I wonder if flooding his suit might have helped?

Most certainly would have helped.

If it was a charcoal heat pack, then the O2 is removed (and should stop the reaction). For either type, the cold water would at least dissipate the heat as well as cooling any burns.

Jon

notdeadyet

24-08-2015, 11:31 AM

As far as I'm aware, these ones are safe. It's just a crystalisation process which gives off the heat, reaching a maximum temp of 130 fahrenheit.

Which is 55degC which is enough to cause a burn. A lot of the HW systems we design are in the zone to kill legionella but not pose a scald risk which if I remember right is 44deg. I've got an exposure chart here and 55deg says 30 seconds exposure to achieve a third degree burn. If one of those ruptured in a drysuit you're in trouble, best you can do is flood the suit but you arent going to do that in 30s.

I tried a kidney belt years ago, mid 90's when they first came out. I remember them being very uncomfortable, fine at first but then you sweat, sweat soaks into your base layer and reaches a similar temp to the pack. Didnt quite reach the burn stage but after a couple of dives I gave it back (test product from a shop I was working with).

Kermit

24-08-2015, 11:36 AM

My understanding is that combustion is controlled by FO2 not PPO2. Am I wrong?

turnerjd

24-08-2015, 11:48 AM

My understanding is that combustion is controlled by FO2 not PPO2. Am I wrong?

At the surface at sea level, yes combustion is controlled by fO2 - although remember that at the surface when fO2 falls or increases, ppO2 does so too. Almost all texts on combustion talk about fO2 as almost nobody starts fires under water at higher ambient pressure.

When absolute pressure changes, it's ppO2 that is important in combustion.

Now, take the example of blowing lots of air at a barbecue to make it go....... What you are doing is locally raising the air pressure by pushing more air in there (as well as replenishing used up O2). The fO2 has stayed the same - it's still 0.21, but the ppO2 has increased a bit from 0.21 to something like 0.3

Or, look at mountaineers - up at very high altitude they have problems with heating as a lot of the burners produce much less heat. Colloquially this is referred to as lack of O2, but it is the low ppO2 - the fO2 at altitude is still 0.21

I hope the examples makes it clear....

Jon

Kermit

24-08-2015, 12:01 PM

At the surface at sea level, yes combustion is controlled by fO2 - although remember that at the surface when fO2 falls or increases, ppO2 does so too. Almost all texts on combustion talk about fO2 as almost nobody starts fires under water at higher ambient pressure.

When absolute pressure changes, it's ppO2 that is important in combustion.

Now, take the example of blowing lots of air at a barbecue to make it go....... What you are doing is locally raising the air pressure by pushing more air in there (as well as replenishing used up O2). The fO2 has stayed the same - it's still 0.21, but the ppO2 has increased a bit from 0.21 to something like 0.3

Or, look at mountaineers - up at very high altitude they have problems with heating as a lot of the burners produce much less heat. Colloquially this is referred to as lack of O2, but it is the low ppO2 - the fO2 at altitude is still 0.21

I hope the examples makes it clear....

Jon

Hi John, I'm really not sure about your BBQ example as I would have thought the effect was soley due to replenishing the depleted O2. But I accept your point about FO2 to a certain extent. I agree, it's not FO2. What I should have said was the amount (moles or whatever) of O2 available in the surrounding gas. Which leads me to the conclusion that increased pressure (and subsequent increase in the amount of O2 in the same volume of gas at lower pressure) would increase the effect of combustion.

Would this be right?

turnerjd

24-08-2015, 12:03 PM

Exactly right. Moles O2 per litre total gas is what is important.

notdeadyet

24-08-2015, 12:30 PM

At the surface at sea level, yes combustion is controlled by fO2 - although remember that at the surface when fO2 falls or increases, ppO2 does so too. Almost all texts on combustion talk about fO2 as almost nobody starts fires under water at higher ambient pressure.

When absolute pressure changes, it's ppO2 that is important in combustion.

Now, take the example of blowing lots of air at a barbecue to make it go....... What you are doing is locally raising the air pressure by pushing more air in there (as well as replenishing used up O2). The fO2 has stayed the same - it's still 0.21, but the ppO2 has increased a bit from 0.21 to something like 0.3

Or, look at mountaineers - up at very high altitude they have problems with heating as a lot of the burners produce much less heat. Colloquially this is referred to as lack of O2, but it is the low ppO2 - the fO2 at altitude is still 0.21

I hope the examples makes it clear....

Jon

Does that hold with flashpoints? A few of the projects I've worked on the design standards were pretty clear on fire safety being dependant on fo2 rather than ppo2. For example air at 5 bar is substantially less of a fire risk than oxygen at 1bar even though the ppo2 remains the same.

turnerjd

24-08-2015, 12:33 PM

Flashpoints? No, I don't think so. I think it is only for sustained open combustion at different pressures.

Jon

dwhitlow

24-08-2015, 01:34 PM

Now, take the example of blowing lots of air at a barbecue to make it go....... What you are doing is locally raising the air pressure by pushing more air in there (as well as replenishing used up O2). The fO2 has stayed the same - it's still 0.21, but the ppO2 has increased a bit from 0.21 to something like 0.3

It was adequately demonstrated in 1995, by George H. Goble, that the best way to get the barbecue going is liquid oxygen. Despite the initial cooling effect the density of oxygen molecules guarantees a rapid result (and wrecks the barbecue).

turnerjd

24-08-2015, 01:39 PM

George H. Goble - Ig Nobel prize in Chemistry 1996............. I remember that, as I was a second year undergrad in Chemistry at Imperial at the time.

Here is the film of it.

https://www.youtube.com/watch?v=sab2Ltm1WcM&noredirect=1

GLOC

24-08-2015, 02:11 PM

More information

http://rnli.org/NewsCentre/Pages/Diver-sustains-serious-burn-when-heat-pad-explodes.aspx

The assistance of the volunteer lifeboat crews at Anstruther were called upon this afternoon (Saturday 22 August) when a diver, diving in an area known as "Wee Bankie" which is approximately 16 miles east of Anstruther sustained chemical burns.
Around 12.20pm today HM Coastguard requested the Anstruther all-weather lifeboat "Kingdom of Fife" launch to assist the skipper of a local dive boat who had called in a report of a diver having been injured. As the story unfolded it became known that the injured diver, a man in his 50's, had sustained a serious chemical burn to his lower back when a heat pad he was wearing under his dive suit to provide relief for muscle spasm had exploded/ignited when he had routinely vented his dive suit with oxygen during his dive.
Diving at a depth of 150 feet, the man, a very experienced diver had to endure a painful controlled and staged ascent to the surface back to the dive boat .
Once at the surface he was assisted into the dive boat where colleagues set about providing first aid and irrigation to the burn.
In response to the pager alert, Morag Morris who is on the Shore crew at Anstruther and a paramedic in her day job arrived at the lifeboat station and was taken out on the Anstruther Inshore Lifeboat to join the crew of the ALB.
On arrival at the scene lifeboat crew provided first aid to the casualty under the supervision of Morag and he was then conveyed to Anstruther Harbour where an ambulance was waiting to transfer him to Ninewells Hospital in Dundee.
Anstruther Lifeboats Operations Manager John Murray commented, " This section of the River Forth around the East Neuk is littered with wrecks and proves to be a very popular location for divers. Every once in a while, like today a diver has a mishap and needs some support or assistance from the RNLI. On this occasion I have to praise the skipper of the local dive boat and the divers themselves for the way in which they remained calm to deal with this situation. They were well equipped and ready to deal effectively with this incident. We are also very lucky at Anstruther to have a paramedic as part of our team. Morag was on scene to assist and this man was handed over to the ambulance crew having received the very best level of first aid".

dwhitlow

24-08-2015, 02:20 PM

a man in his 50's, had sustained a serious chemical burn to his lower back when a heat pad he was wearing under his dive suit to provide relief for muscle spasm had exploded/ignited when he had routinely vented his dive suit with oxygen during his dive.

:OMG: Maybe the curry from the night before had a contribution to make!

I hope the oxygen bit is an error!

Kermit

24-08-2015, 02:24 PM

:OMG: Maybe the curry from the night before had a contribution to make!

I hope the oxygen bit is an error!

It's not unheard of for people to use O2 as a suit inflate. Stupid but that hasn't stopped people doing it in the past.

rubber chicken

24-08-2015, 02:41 PM

I remember dropping one of the gel packs down the back of my wetsuit just prior to a, 14-15c, river dive. Dumb idea, before I could get into my harness, i was off down the bank and straight into the water. Jeez, that thing got hot.
I had another go, next day, but this time waited until I was kitted up and at the waters edge. Waste of time, it only warmed a very small bit and that for only about 10 minutes. I gave up on them and bought a Sharkskin top instead.

turnerjd

24-08-2015, 03:12 PM

Did a quick Google search on this incident.....

I know it's the DailyWail, but....

Diver trapped 160 feet under the sea in agony when therapeutic heat pad on his back exploded (http://www.dailymail.co.uk/news/article-3208690/Diver-suffered-chemical-burns-freak-accident-therapeutic-heat-pad-exploded-160ft-sea-level.html)

The images do not look nice at all.

Jon

PS sorry for polluting you with the Wail....

GLOC

24-08-2015, 03:18 PM

A real shame and looks like a nasty injury, but talk about media-related bollocks though!

The disaster unfolded on Saturday when he was using gas enriched with oxygen instead of the oxygen tank he normally uses. But when he vented his dry suit, the gas reacted with the chemical in the heat pack.| DailyMail on Facebook

turnerjd

24-08-2015, 03:20 PM

Have to admit the DailyWail is a bit like a comic book.

Look at the pictures, but whatever you do, don't read the words.

Jon

Barrygoss

24-08-2015, 03:23 PM

A real shame and looks like a nasty injury, but talk about media-related bollocks though!

or he was using a nitrox mix instead of his normal air...

B

dwhitlow

24-08-2015, 03:26 PM

Look at the pictures, but whatever you do, don't read the words.

Ouch! If only he'd though to quench it through the neck seal!

PeterL

24-08-2015, 03:36 PM

There was also a guy that got pretty bad burns on a dive to the Lucitania (90m) a few years ago. The pack didnt burst but seemingly the higher ppo2 inside his suit caused a much stronger chemical reaction than normal

According to those around the Irish event the pack burnt clear out of the dry suit, that's a first degree burn then a full suit flood for 3H or so.
That's just not going to be a good day....

turnerjd

24-08-2015, 03:37 PM

that's a first degree burn....

First degree?

More like third degree, no?

Jon

PeterL

24-08-2015, 03:37 PM

Ouch! If only he'd though to quench it through the neck seal!

would have been some acrobatics to get water to that spot......

PeterL

24-08-2015, 03:38 PM

First degree?

More like third degree, no?

Jon

Yup, perhaps second, perhaps third, depends how quick the water got to it :)

jturner

24-08-2015, 03:42 PM

Does that hold with flashpoints? A few of the projects I've worked on the design standards were pretty clear on fire safety being dependant on fo2 rather than ppo2. For example air at 5 bar is substantially less of a fire risk than oxygen at 1bar even though the ppo2 remains the same.

OT but I imagine the raised ambient pressure will affect the material's vapour pressure somewhat, which would in turn impact the flashpoint?

diverdave

24-08-2015, 08:17 PM

He was using his 50% deco gas for his suit . Certainly won't do that again. Shame as he missed a great dive 😃

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robw679

24-08-2015, 09:41 PM

Going out on a limb here..............but........how.....about.....a.. ....
Decent undersuit....????????????

hippytyre

24-08-2015, 10:16 PM

For lower back pain?

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turnerjd

25-08-2015, 04:58 AM

For lower back pain?

I've had lower back pain whilst diving before.... Solution was proper weighting (losing a couple of kgs), changing where is was placed, and changing stab so that everything was correctly placed.... Not a chemical heat pack.

Jon

matt yates

25-08-2015, 05:46 AM

Did he use deep heat

hippytyre

25-08-2015, 06:36 AM

I've had lower back pain whilst diving before.... Solution was proper weighting (losing a couple of kgs), changing where is was placed, and changing stab so that everything was correctly placed.... Not a chemical heat pack.

Jon
You're probably right but I was replying to the suggestion that a decent under suit would help back pain.

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Paulo

25-08-2015, 08:34 AM

this was liked elsewhere.

It deals with the incident on the Lusi that I mentioned earlier.

http://www.irishexaminer.com/ireland/health/surgeon-warns-against-use-of-heat-packs-in-sea-diving-after-freak-accident-110012.html

Pat Coughlan

25-08-2015, 07:12 PM

According to those around the Irish event the pack burnt clear out of the dry suit, that's a first degree burn then a full suit flood for 3H or so.
That's just not going to be a good day....

Yes it was a charcoal pack and no it didnt burn through his drysuit.

There is a lot of posts regarding the dangers of using heat packs and battery operated heat vests where the battery is stored under the drysuit over on Burger World and well worth a read. Long story short if you are going to think of using a suit heating system where you cannot control the reaction or switch it off........dont!

Cheers Pat

Pat Coughlan

25-08-2015, 07:17 PM

There was also a guy that got pretty bad burns on a dive to the Lucitania (90m) a few years ago. The pack didnt burst but seemingly the higher ppo2 inside his suit caused a much stronger chemical reaction than normal

Paulo half a story as usual, it was a ferrous oxide heat pack, the Fo2 and PP02 caused the reaction to become uncontrolled and the pack did rupture

Cheers Pat

PeterL

25-08-2015, 07:53 PM

Paulo half a story as usual, it was a charcoal heat pack, the Fo2 and PP02 caused the reaction to become uncontrolled and the pack did rupture

Cheers Pat

Howdy Pat, hope all's well..... :)

Nice one, was it a charcoal heat stick or a FE Oxide type, I presume from your comments that it's the old school light the stick in the box type? Very very not clever but from this thread not the only way to cook your nuts :)

Pat Coughlan

25-08-2015, 08:04 PM

Howdy Pat, hope all's well..... :)

Nice one, was it a charcoal heat stick or a FE Oxide type, I presume from your comments that it's the old school light the stick in the box type? Very very not clever but from this thread not the only way to cook your nuts :)

Hey Pete All good here hope you and the Aurora are doing well

The heat pack was the ferrous oxide type I edited post :-)

PeterL

25-08-2015, 08:06 PM

Hey Pete All good here hope you and the Aurora are doing well

The heat pack was the ferrous oxide type

OK so the same as this burn. When will some people learn. :)

Aurora is awesome, it and I been to 115M, exploring unknown wrecks and doing some very very awesome dives this year. Morgan is still keen to get me back north but it's been too good a year to date.

Pat Coughlan

25-08-2015, 08:21 PM

OK so the same as this burn. When will some people learn. :)

Aurora is awesome, it and I been to 115M, exploring unknown wrecks and doing some very very awesome dives this year. Morgan is still keen to get me back north but it's been too good a year to date.

Its a sweet unit for sure

With regard to learning there is information out there if you go looking but if you are not a forum surfer and not up to speed on chemistry then it can, and has happened all to easily.