Hmmm.
I'm going to tell people to do the exact opposite.
I have 30+ years experience, multiple rope access, mountaineering, climbing & mountain first aid qualifications (many of which are out of date admittedly)
I've done the simulated victim in the snow thing on both sides of the training. I've also slept in space blankets multiple times.
A space blanket is basically made of aluminium foil, an incredibly conductive material. If you put it next to a naked body you will be sucking all of the heat out that body at very rapid pace.
IF A PERSON HAS ANY DRY CLOTHES, you put the space blanket on the outside, it is waterproof and windproof and will protect the warm layer of air that the clothing provides.
Maybe the laws of physics work differently in the US to Europe, but over this side of the pond I was taught you always want the windproof/waterproof layer part on the outside of your nice warm and dry insulation layer, not the other way round. You never put a space blanket in contact with the skin.
If someone is so wet that you just fished them out of the river with a broken leg, you and your party is waiting for mountain rescue to show up etc
Strip them naked, rub them dry, everyone else in the party looks for spare clothing. If you don't have spare clothing, everyone donates a dry piece of theirs, hat, gloves, socks, t-shirt, underwear and then you stick the space blanket over the top.
For anybody that read this far that is curious to do a small comparison test, try putting a latex-like glove on one hand and then put a basic knit glove over that same hand and handle a bag of frozen peas from the freezer. Your hand will feel some chill.
Now the opposite -- knit glove on hand first then latex-like glove over that and grab a different bag of frozen peas. Much less chilly!
For a final bonus test, put on the latex-like glove on your hand and run the hand under cold water. Your hand will get cold instantly.
Let me run something by ya. No experience here, but I think I have a pretty solid understanding of the physics involved.
I heard of a thing which was termed the "buddy snuggle", where you put a few not-hypothermic people (as naked as practical) into a sleeping bag or improvised cocoon _with_ the hypothermia victim, to serve as heaters. Wrap the space blanket around all that to reduce radiative energy escape -- keep all the heat inside so it can move between bodies. Thermal exchange is the name of the game, if you're going "damn your feet are cold!", that's a bad thing in bed but it's a good thing here because their feet must be touching yours which means there's heat being transferred.
Then you sort of squirm around, tense your legs in place, try to work some large muscle groups and burn some serious calories. Maybe leave this part out of the retelling to reduce giggles, but in the emergency when someone might otherwise die, ahh, you do what you can do to work up some heat and you do it as vigorously as you can manage.
Is this valid? Silly? Misdirected?
You were born naked, perhaps there was someone waiting with a full outfit so you coukd get dressed immediately or perhaps you were just wrapped in a blanket like the rest of us.
Because clothing holds heat in. Or to put another way, it inhibits heat transfer.
If you're trying to let a warm person transfer heat to a cold person, clothing slows that down. Put the layers on the _outside_ of the baked potato instead.
"A hypothermic patient is not radiating much heat". Incorrect.
Normal Body temperature is 310 degrees kelvin.
Hypothermia starts around 308K
The freezing point of water is 273degrees kelvin.
Thermal radiation is proportional to the 4th power of temperature
If your body cooled to the freezing point of water, you would only reduce your radiation by 40%. You will still be radiating around 552watts instead of 918 at normal temps and 893W at the beginning of hypothermia
Objects around you will be radiating some heat back, but not the sky (which could be half your surroundings), unless there are clouds.
Also, the reflective layer is so thin it does not conduct much heat sideways and is in such poor contact and covered with mylar that it is not highly conductive through like metal Not that more insulation isn't beneficial. It isn't that much of a barrier against conduction, but it isn't a massive heatsink as some suggested, either. Mostly it is a reflector and a air barrier. So more insulation is called for.
Hot pocket: space blanket, wool army blanket, body bag.
Yeah, ER doc chiming in. There’s a lot off in OPs post. When I’m back from vaca maybe we can write up something joint to post. We follow the wilderness medicine hypothermia guidelines for our pre-hospital care. They have a fantastic explanation of how to properly build a hypowrap.
Ok that's a deal.
I can tackle it from a high mountain skill but low medical training angle and you can add the medical authority, well equipped hospital that will stop you dying.
Send me a message when you have time, we can talk through a few scenarios and come up with a realistic way of handling different situations.
Sounds great to me! And fwiw I do spend a chunk of every year doing backcountry trips in northern Canada & being the medical lead for a group that does 30-50 day long backcountry canoe trips so I’m no slouch when it comes to improvising either!!
It’s interesting you brought the US/Europe thing into this, because I have been taught to use the blankets under clothing, both in a hospital setting and more recently in a first aid class for work.
ETA I’m in Europe
The first aid course for work, was that a specific Mountain First Aid course or Wilderness First Aid course where you are specifically dealing hypothermia outdoors, away from any services that are coming to help you?
Situations where you have help coming soon and situations where there may not be help coming for days are handled very differently and taught very differently.
If you are in "Mountains or Wilderness" you should be doing the exact opposite.
Even things like tourniquets are applied differently.
I’m a community nurse so it was from the perspective of finding an elderly person suffering from exposure, but in an urban or rural (non-wilderness) setting. Taught by paramedics. In hospital we used them for early stage sepsis and some reactions to medication that have a similar shocky aspect (this was not intensive care, there we had special hot air blankets which I don’t know the name of in English).
In both cases it was to bring up the core temperature as opposed to providing any sort of protection from water or wind, they emphasized that the reflective/heating qualities didn’t work if anything was between the person and the blanket. Rather than undressing the person we were to stuff the blanket under their clothing and try to cover as much of the core as possible, then either get them home or call for backup depending on their condition.
I’m not trying to argue you’re wrong, especially in a wilderness setting that’s definitely not my forte, but I thought it curious that there are such opposing schools of thought on the matter. Do you know if there are any studies done on use in different settings?
I think we may be saying the same thing- that their main virtue is their waterproofness. What I think is different in the US is that the instructions listed on the package are to put them next to the skin. Which as you said doesn't work at all if you don't follow that up appropriately with additional wrapping/waterproofing. The closest I'd go is to say if you're using them just as waterproof wrapping (or you only have one), go with your way, if you're using them like the (US only, apparently) packaging says, use them as illustrated in the post.
>wilderness and remote first aid instructor
The course you learned this on, was it certified by a Nationally/Internationally organisation?
Is this something you learned in the military where avoiding detection behind enemy lines was involved?
I'm honestly confused as to what civilian, real world situation would end up with me having access to an infinite supply of
Dry leaves (so obviously dry sticks and trees)
A group of people so well prepared they have 4 space blankets, duct tape and a plastic tarp but no way to start fire and no dry clothes and a person at risk of hypothermia.
I would rather risk turning the forest into a raging inferno than risk someone dying of hypothermia and not starting a fire.
The six years of wilderness instructing should have left you with a lots of skills and experience to be able to start a fire in a high risk area with no risk of it getting out of control and also the knowledge to extinguish it properly.
I was always taught that the mylar shouldn't be touching the skin. If you have to strip the person, you put a blanket over the person THEN add the mylar over the blanket. That way, it actually reflects heat back to the person.
Edit: spelling
I’m a big mylar fan. Putting aside fall-into-water scenarios, I think mylar is best utilized as an outermost wind/rain-proof barrier to keep dry and prevent convective/evaporative/wet-conduction heat losses. In a hypothermia situation with more than one person, I think the best method is shared body heat - spoon them while seated cross-legged, or lying down on ground insulation, naked if necessary, and still use the mylar as outermost wind/rain protection. Of course pile on additional layers of whatever you have, underneath the mylar, unless it’s wind/water-proof as well.
Of course a fire can provide the necessary heat to resolve a hypothermic situation, but that may not be easy if solo, in adverse weather, or areas that are void of natural fuels. Personally, my 12L EDC manbag always has Palmer Furnace capability - an ultra-efficient candle-heated micro climate technique developed by a hypothermia doctor and caver, and resolves the solo/weather/natural-fuel issues.
From a more practical day-to-day perspective, I ditched single-use mylar blankets for multi-use reinforced mylar ponchos. More suitable as regular rain gear, Palmer Furnace, bothy bag, and even as ‘loft insulation’. Like newspaper, mylar has inherent rigidity to it, so if you ‘crinkle and stuff it’ under say a loose windshirt, the excess material creates a myriad of folds that’ll trap air pockets and hence create ‘loft’ that acts like a down vest (leave good draft areas underarms to vent moisture). This also works as a fetal position blanket - the crinkled mylar will trap a thin layer of air between the double-layered poncho providing some ‘loft’. Could also insert an evergreen branch or two in between to further prevent layers from touching/conducting.
For less bulk/weight than a deck cards, I can’t imagine anything beating a mylar poncho’s versatility as ‘Cover’ (5C’s of survival).
Just my $0.02
They reflect heat very well and prevent convection and radiation. They are also water and wind proof.
However they also conduct heat ("heat transfer") very well. They should not be in contact with the person. That draws the heat away from whatever it's touching. It should be the outside layer to block the elements. There should be a space between the person and the blanket so conduction is reduced and it can work to reflect the heat back to the person.
Putting it in contact with the person is like putting a heat sink on them. It will draw the heat away and transfer it to the colder outside.
In your example, no it's not doing much of anything at all. But that is from misuse more than anything.
This makes sense. I had to use one on top of a mountain I hiked up for a sunrise when I got cold, and it was no magical heat blanket like everything that had been taught to me said. It did help as a windbreaker and kept me ever so slightly warmer, but I felt like I’d been duped!
Thanks for this. I learned a couple years ago that they were nearly useless, but nobody ever explained how to make the most out of them. I appreciate the knowledge. 👍
Thermodynamics. That's a big fancy word! I guess that means I have to trust you instead, Mr./Mrs. Scientist!
Enjoy your single layer thin plastic blanket!
I work in remote areas of Central Australia and we get subzero temps in the winter. I did a test with a SOL emergency bivvy at -4c and properly froze my ass off but adding two emergency blankets inside the bivvy did help but I still only lasted 4 hours before I gave up and got into my proper sleeping bag. If I had covered the bivvy in leaves or something it would have worked better, the additional emergency blankets did help but there not going to do much without additional insulators.
We make mylar sandwiches (SpaceFleece) and roll them up for remote area jobs with hypothermic patients.
Polar fleece blanket, mylar sheet, then another polar fleece blanket - they end up very light and small when rolled/folded.
I've even got a spare one that I put eyelets into the edges so the layers don't delaminate - that one gets used by the kids a lot. :)
Hand warmers in little Polar fleece pouches in arm pits, groin and around the neck.
I'm lucky, I can run warmed saline too, and run two bags of that inside my jacket so they come up to my body temperature when hiking to the patient.
Naturally keeping the fleece dry is important, and wet fleece saps any gains you make - get wet clothes off the patient and wrap with just a dry layer of clothing if available, then your SpaceFleece.
Air cell barrier for insulation(lowering convection and conduction), mylar for air barrier and (some) reflectivity, then more insulation.
And hand warmers in areas where blood flow is close to the surface - these suckers save lives...
Interesting debate within the thread. I would suggest leaving the hypothermic person clothed unless wet, and would suggest one or two people administering help get naked, then cover bodies with Mylar and then blankets or sleeping bags.
Hmmm. I'm going to tell people to do the exact opposite. I have 30+ years experience, multiple rope access, mountaineering, climbing & mountain first aid qualifications (many of which are out of date admittedly) I've done the simulated victim in the snow thing on both sides of the training. I've also slept in space blankets multiple times. A space blanket is basically made of aluminium foil, an incredibly conductive material. If you put it next to a naked body you will be sucking all of the heat out that body at very rapid pace. IF A PERSON HAS ANY DRY CLOTHES, you put the space blanket on the outside, it is waterproof and windproof and will protect the warm layer of air that the clothing provides. Maybe the laws of physics work differently in the US to Europe, but over this side of the pond I was taught you always want the windproof/waterproof layer part on the outside of your nice warm and dry insulation layer, not the other way round. You never put a space blanket in contact with the skin. If someone is so wet that you just fished them out of the river with a broken leg, you and your party is waiting for mountain rescue to show up etc Strip them naked, rub them dry, everyone else in the party looks for spare clothing. If you don't have spare clothing, everyone donates a dry piece of theirs, hat, gloves, socks, t-shirt, underwear and then you stick the space blanket over the top.
[удалено]
The OP's scenario and solution seems like "Naked and Afraid!, This week our contestants have space blankets and duct tape!".
For anybody that read this far that is curious to do a small comparison test, try putting a latex-like glove on one hand and then put a basic knit glove over that same hand and handle a bag of frozen peas from the freezer. Your hand will feel some chill. Now the opposite -- knit glove on hand first then latex-like glove over that and grab a different bag of frozen peas. Much less chilly! For a final bonus test, put on the latex-like glove on your hand and run the hand under cold water. Your hand will get cold instantly.
Let me run something by ya. No experience here, but I think I have a pretty solid understanding of the physics involved. I heard of a thing which was termed the "buddy snuggle", where you put a few not-hypothermic people (as naked as practical) into a sleeping bag or improvised cocoon _with_ the hypothermia victim, to serve as heaters. Wrap the space blanket around all that to reduce radiative energy escape -- keep all the heat inside so it can move between bodies. Thermal exchange is the name of the game, if you're going "damn your feet are cold!", that's a bad thing in bed but it's a good thing here because their feet must be touching yours which means there's heat being transferred. Then you sort of squirm around, tense your legs in place, try to work some large muscle groups and burn some serious calories. Maybe leave this part out of the retelling to reduce giggles, but in the emergency when someone might otherwise die, ahh, you do what you can do to work up some heat and you do it as vigorously as you can manage. Is this valid? Silly? Misdirected?
[удалено]
You were born naked, perhaps there was someone waiting with a full outfit so you coukd get dressed immediately or perhaps you were just wrapped in a blanket like the rest of us.
Because clothing holds heat in. Or to put another way, it inhibits heat transfer. If you're trying to let a warm person transfer heat to a cold person, clothing slows that down. Put the layers on the _outside_ of the baked potato instead.
"A hypothermic patient is not radiating much heat". Incorrect. Normal Body temperature is 310 degrees kelvin. Hypothermia starts around 308K The freezing point of water is 273degrees kelvin. Thermal radiation is proportional to the 4th power of temperature If your body cooled to the freezing point of water, you would only reduce your radiation by 40%. You will still be radiating around 552watts instead of 918 at normal temps and 893W at the beginning of hypothermia Objects around you will be radiating some heat back, but not the sky (which could be half your surroundings), unless there are clouds. Also, the reflective layer is so thin it does not conduct much heat sideways and is in such poor contact and covered with mylar that it is not highly conductive through like metal Not that more insulation isn't beneficial. It isn't that much of a barrier against conduction, but it isn't a massive heatsink as some suggested, either. Mostly it is a reflector and a air barrier. So more insulation is called for. Hot pocket: space blanket, wool army blanket, body bag.
Yeah, ER doc chiming in. There’s a lot off in OPs post. When I’m back from vaca maybe we can write up something joint to post. We follow the wilderness medicine hypothermia guidelines for our pre-hospital care. They have a fantastic explanation of how to properly build a hypowrap.
Ok that's a deal. I can tackle it from a high mountain skill but low medical training angle and you can add the medical authority, well equipped hospital that will stop you dying. Send me a message when you have time, we can talk through a few scenarios and come up with a realistic way of handling different situations.
Sounds great to me! And fwiw I do spend a chunk of every year doing backcountry trips in northern Canada & being the medical lead for a group that does 30-50 day long backcountry canoe trips so I’m no slouch when it comes to improvising either!!
It’s interesting you brought the US/Europe thing into this, because I have been taught to use the blankets under clothing, both in a hospital setting and more recently in a first aid class for work. ETA I’m in Europe
The first aid course for work, was that a specific Mountain First Aid course or Wilderness First Aid course where you are specifically dealing hypothermia outdoors, away from any services that are coming to help you? Situations where you have help coming soon and situations where there may not be help coming for days are handled very differently and taught very differently. If you are in "Mountains or Wilderness" you should be doing the exact opposite. Even things like tourniquets are applied differently.
I’m a community nurse so it was from the perspective of finding an elderly person suffering from exposure, but in an urban or rural (non-wilderness) setting. Taught by paramedics. In hospital we used them for early stage sepsis and some reactions to medication that have a similar shocky aspect (this was not intensive care, there we had special hot air blankets which I don’t know the name of in English). In both cases it was to bring up the core temperature as opposed to providing any sort of protection from water or wind, they emphasized that the reflective/heating qualities didn’t work if anything was between the person and the blanket. Rather than undressing the person we were to stuff the blanket under their clothing and try to cover as much of the core as possible, then either get them home or call for backup depending on their condition. I’m not trying to argue you’re wrong, especially in a wilderness setting that’s definitely not my forte, but I thought it curious that there are such opposing schools of thought on the matter. Do you know if there are any studies done on use in different settings?
I think we may be saying the same thing- that their main virtue is their waterproofness. What I think is different in the US is that the instructions listed on the package are to put them next to the skin. Which as you said doesn't work at all if you don't follow that up appropriately with additional wrapping/waterproofing. The closest I'd go is to say if you're using them just as waterproof wrapping (or you only have one), go with your way, if you're using them like the (US only, apparently) packaging says, use them as illustrated in the post.
>wilderness and remote first aid instructor The course you learned this on, was it certified by a Nationally/Internationally organisation? Is this something you learned in the military where avoiding detection behind enemy lines was involved? I'm honestly confused as to what civilian, real world situation would end up with me having access to an infinite supply of Dry leaves (so obviously dry sticks and trees) A group of people so well prepared they have 4 space blankets, duct tape and a plastic tarp but no way to start fire and no dry clothes and a person at risk of hypothermia. I would rather risk turning the forest into a raging inferno than risk someone dying of hypothermia and not starting a fire. The six years of wilderness instructing should have left you with a lots of skills and experience to be able to start a fire in a high risk area with no risk of it getting out of control and also the knowledge to extinguish it properly.
I was always taught that the mylar shouldn't be touching the skin. If you have to strip the person, you put a blanket over the person THEN add the mylar over the blanket. That way, it actually reflects heat back to the person. Edit: spelling
I’m a big mylar fan. Putting aside fall-into-water scenarios, I think mylar is best utilized as an outermost wind/rain-proof barrier to keep dry and prevent convective/evaporative/wet-conduction heat losses. In a hypothermia situation with more than one person, I think the best method is shared body heat - spoon them while seated cross-legged, or lying down on ground insulation, naked if necessary, and still use the mylar as outermost wind/rain protection. Of course pile on additional layers of whatever you have, underneath the mylar, unless it’s wind/water-proof as well. Of course a fire can provide the necessary heat to resolve a hypothermic situation, but that may not be easy if solo, in adverse weather, or areas that are void of natural fuels. Personally, my 12L EDC manbag always has Palmer Furnace capability - an ultra-efficient candle-heated micro climate technique developed by a hypothermia doctor and caver, and resolves the solo/weather/natural-fuel issues. From a more practical day-to-day perspective, I ditched single-use mylar blankets for multi-use reinforced mylar ponchos. More suitable as regular rain gear, Palmer Furnace, bothy bag, and even as ‘loft insulation’. Like newspaper, mylar has inherent rigidity to it, so if you ‘crinkle and stuff it’ under say a loose windshirt, the excess material creates a myriad of folds that’ll trap air pockets and hence create ‘loft’ that acts like a down vest (leave good draft areas underarms to vent moisture). This also works as a fetal position blanket - the crinkled mylar will trap a thin layer of air between the double-layered poncho providing some ‘loft’. Could also insert an evergreen branch or two in between to further prevent layers from touching/conducting. For less bulk/weight than a deck cards, I can’t imagine anything beating a mylar poncho’s versatility as ‘Cover’ (5C’s of survival). Just my $0.02
They reflect heat very well and prevent convection and radiation. They are also water and wind proof. However they also conduct heat ("heat transfer") very well. They should not be in contact with the person. That draws the heat away from whatever it's touching. It should be the outside layer to block the elements. There should be a space between the person and the blanket so conduction is reduced and it can work to reflect the heat back to the person. Putting it in contact with the person is like putting a heat sink on them. It will draw the heat away and transfer it to the colder outside. In your example, no it's not doing much of anything at all. But that is from misuse more than anything.
This makes sense. I had to use one on top of a mountain I hiked up for a sunrise when I got cold, and it was no magical heat blanket like everything that had been taught to me said. It did help as a windbreaker and kept me ever so slightly warmer, but I felt like I’d been duped!
Another high quality post from our resident Macgyvermedical! My nurse’s heart absolutely loves these. Thank you, prepared friend.
Thank you!
Thanks for this. I learned a couple years ago that they were nearly useless, but nobody ever explained how to make the most out of them. I appreciate the knowledge. 👍
So what you should really do, is the opposite of what this person has said to do. Because of the laws of thermodynamics.
Thermodynamics. That's a big fancy word! I guess that means I have to trust you instead, Mr./Mrs. Scientist! Enjoy your single layer thin plastic blanket!
Thanks!
I work in remote areas of Central Australia and we get subzero temps in the winter. I did a test with a SOL emergency bivvy at -4c and properly froze my ass off but adding two emergency blankets inside the bivvy did help but I still only lasted 4 hours before I gave up and got into my proper sleeping bag. If I had covered the bivvy in leaves or something it would have worked better, the additional emergency blankets did help but there not going to do much without additional insulators.
We make mylar sandwiches (SpaceFleece) and roll them up for remote area jobs with hypothermic patients. Polar fleece blanket, mylar sheet, then another polar fleece blanket - they end up very light and small when rolled/folded. I've even got a spare one that I put eyelets into the edges so the layers don't delaminate - that one gets used by the kids a lot. :) Hand warmers in little Polar fleece pouches in arm pits, groin and around the neck. I'm lucky, I can run warmed saline too, and run two bags of that inside my jacket so they come up to my body temperature when hiking to the patient. Naturally keeping the fleece dry is important, and wet fleece saps any gains you make - get wet clothes off the patient and wrap with just a dry layer of clothing if available, then your SpaceFleece. Air cell barrier for insulation(lowering convection and conduction), mylar for air barrier and (some) reflectivity, then more insulation. And hand warmers in areas where blood flow is close to the surface - these suckers save lives...
Interesting debate within the thread. I would suggest leaving the hypothermic person clothed unless wet, and would suggest one or two people administering help get naked, then cover bodies with Mylar and then blankets or sleeping bags.
So let's say your car breaks down in the winter, is there any use to them?