Hazards: Cold. Of wind double-dipping, clothes into water single-dipping et al.

[Anthony]

Originally Posted by Celjabba

Honestly, I have no idea, but it is a nice simmetry rules wise, and it avoid the possibly counter-intuitive result of being better naked than in wet clothing in sub-zero temp...

You're generally better off naked than in wet cloth, because being wet is worse than being naked (evaporative cooling is really fast, and wet cloth is lousy insulation) and cloth holds more water than can cling to your skin and thus takes longer to dry.

[Peter Knutsen]

Originally Posted by Celjabba

Honestly, I have no idea, but it is a nice simmetry rules wise, and it avoid the possibly counter-intuitive result of being better naked than in wet clothing in sub-zero temp... Inside the comfort zone, it is definitively better, no discussion.

I think that in my Ärth historical fantasy setting, spellcasters using magic to boost their cold tolerance (as in many levels of Temperatur Tolerance vs Cold, PM -10% Arcane Magic, in GURPS terms) will quite often go naked.

Part of that is in order to make a statement ("I am uber cool!", and yes the male wizard walking nekkid through a snow storm is an in-setting trope), but I think a larger part of it is practicality: Moisture often accompanies cold, and moisture clings to cloth, whereas it doesn't cling to bare skin. Sweating under clothes, when it is very cold, can also complicate things dangerously - being start raving naked removes that concern.

More generally, it might be beneficial to contemplate how special or unusual effects will interact with the normal rules for cold/water/exposure, although it is quite possible that the interactions will turn out to be good even if just simply extrapolated from the basic assumptions. It's not a given that a tonne of speshul case rules will be necessary.

But if so, it's not just for magic, psionics and chi, but also for biological species traits, as in genetic engineering or as in non-terrestrial alien species. Or even non-engineered terrestrial species with bodies that do things very differently from how our Human bodies do them, such as cetaceans.

[Edris]

Originally Posted by Vicky

Thanks.

Also, weird coincidence: my survival-oriented questions are mostly related to preparing to play a survival-oriented character in an upcoming campaign; and the most likely name for the character was/is Edris (picked maybe a month or a half ago).

Hah, how funny. I've been using Ceris/Edris for various gaming things for the better part of a decade or so now. Ceris is for int/dex, Edris is for str/ht style characters respectively.

Originally Posted by Varyon

Yeah, this is due to a simplification on GURPS's part. Realistically, exposure isn't necessary for frostbite to come into play - you simply have to be losing enough body heat (be it due to direct exposure or inadequate protection) for the body to start basically shunting heat from the extremities to protect the core. A better rule might be to simply state that once you've taken over FP/2 or so in FP damage from cold, further cold damage means a roll against HT - failure causes equal HP damage to both hands and both feet. Having the fingers/toes exposed - or worse, wet - gives an HT penalty against the crippling effect. Characters can attempt to protect their digits by breathing on them, rubbing them together, etc - the reason toes get frostbite so frequently is because you'd have to sit down and take your boots off to keep them warm.


As Edris noted, a lot of the damage from actual freezing is due to formation of ice crystals, which will rip cells apart. A decent number of cells typically luck out and don't get damaged beyond repair during a freeze, however, so when you thaw them out they can start up functions again. Continually freezing and then thawing the cells will result in far more loss of function - if 80% of cells survive each freezing (this is probably a rather high number above cryogenic temperatures - the longer it takes to freeze the more cells will die), then one freezing kills off 20%, two freezings kill off 36%, three freezings kill off nearly 50%, and so forth.

Yeah, frostbite doesn't require exposure; you'll freeze if it gets cold enough even if you're covered up. Though, technically, you could explain that with hypothermia adding damage tallies to every body part for crippling purposes as well.

Originally Posted by Varyon

Frostbite should probably be 1 HP of damage to each finger and toe (or, rather, each hand and foot, as fingers and toes aren't legitimate targets in GURPS), but either no HP loss overall or only 1 HP loss overall. Thus, at 8 HP of frostbite injury, all of the character's hands and feet have been permanently crippled beyond recovery (they've hit the "severed" category of damage). Note, however, that at a mere 4 HP of frostbite injury the hands and feet are crippled, with an HT roll to see how long it will take - if it will indeed be possible at all - to recover.

The raw frostbite text says that any exposed location takes 1 HP of damage per FP lost to hypothermia. Personally I take this as every exposed extremity takes an HP of damage. Also, keep in mind that if you're using martial arts locations, frostbite also effects your nose, ears, and cheeks realistically. I'd think about using either use the Last Wounds rules (Campaigns P.420) or state that these tallies are for crippling purposes only and you only take 1 "real" HP of damage regardless of locations covered just because the entire idea behind losing extremity/limb blood flow is to keep you alive; it would be counter-intuitive if it killed you vastly faster in my opinion. I'm pretty sure it is Large Area Injury now that I think about it, consider opinions on crippling and record keeping there.

Though, you still might have to deal with the gangrene and other infections afterwards anyway..

Also, you should look up case studies and/or pictures of frostbite. Really nasty stuff, it's considered a medical emergency and uses the same tables for tissue damage as burns; you can actually wind up in a burn ward for frostbite as well, since the damage and complications are similar.

Originally Posted by Varyon

This is the case to the best of my knowledge. Both lowering the temperature and increasing the rate of FP loss are good ways of representing this effect, but applying both really is double-dipping.

As an unrelated note, I actually can't find where actual wind-chill rules are. Could anyone point out how much wind effects temperature?

Originally Posted by Vicky

Wet clothing gives an additional -5 to HT checks to resist cold, which is as bad as no clothing (apparently except in the case of arctic clothing, which has an inherent +5, resulting in +0 . . . I don't think it makes sense, but maybe I'm wrong). Anyway, I did once hear in some natgeo-clone show that getting out of wet clothes is a #1 priority but . . . is it really better to strip naked after climbing onto the shore from under the ice? It seems rather dubious to me, but I know next to nothing about outdoor survival. (Yes, I do realise that getting a fire-and-shelter is a priority; I am also asking these questions on the assumption that the adventurer has the sorts of stats and/or situation that these events aren't an immediate death sentence, but still a serious threat to life and limb.)

I actually forgot to touch on this. Going from liquid to gas is an endothermic reaction, it will cool the nearby environment. It's like a swamp cooler, it's not going to keep any warmth inside your body/clothing effectively because of the cooling action. This is evident in that wet, light clothes is actually -10 HT, because it's going to cool you really fast, faster then going without them. Effectively, you have more than double the surface area, and one of those surfaces holds a lot of water, so you're going to cool significantly faster. Arctic clothing generally has at least a double layer with waterproofing on at least one layer, it's going to be pretty good at keeping wet out and warmth in even while some of it is wet. Even if the entire outfit is wet, the inside of it is going to be hard pressed to do very much drying when it's sealed up so well; think about a water bottle, how much evaporation do you see inside a sealed bottle? So it's not as nearly as bad as wet normal clothing, or heaven forbid, wet light clothing.

[Flyndaran]

It should cool faster, but also dry faster, I would think.

Arctic clothing is most certainly not automatically waterproof as no sane clothier assumes you'll dive into ice water.

Cheap LIGHT waterproofing is rather high tech.

[vicky_molokh]

Originally Posted by Flyndaran

Cheap LIGHT waterproofing is rather high tech.

A waterproofed parka is TL0, 11lbs, while a non-waterproofed one is 10lbs. Big deal.

[Flyndaran]

Originally Posted by vicky_molokh

A waterproofed parka is TL0, 11lbs, while a non-waterproofed one is 10lbs. Big deal.

I never heard of arctic peoples making all their clothes that way. Not doing so must have killed countless over the years from momentary dunks and subsequent hypothermia.

Am I wrong, and everybody really does make clothes that way in cold climes?

[Anthony]

Originally Posted by vicky_molokh

A waterproofed parka is TL0, 11lbs, while a non-waterproofed one is 10lbs. Big deal.

What GURPS Low-Tech calls 'waterproof' is what we would call 'water-resistant'; it's designed to protect against rain, not immersion (boot wax is the same technology being described in low tech. Waxing your boots does not turn them into waders). Clothing suitable for surviving a dive into arctic water is TL 7 (a neoprene wetsuit, for example).

[Edris]

Originally Posted by Flyndaran

It should cool faster, but also dry faster, I would think.

Arctic clothing is most certainly not automatically waterproof as no sane clothier assumes you'll dive into ice water.

Cheap LIGHT waterproofing is rather high tech.

Arctic clothing is not light. And the portion of arctic clothing being water and windproof comes from high tech to begin with, no one mentioned tech level until you, actually; although Vicky already covered low tech options. Cotton is also notorious for staying wet for a long time amongst survivalists, typically you want synthetics.

In any case, it's not suppose to keep you dry in the water to begin with, it's just to help if you happen to get wet. Dry suits are indeed TL7 as indicated in the high-tech (P.75) book and by Anthony, but it only protects against thermal shock. You still need suitable cold resistant clothing underneath.

[Bruno]

On the subject of frostbite, reduced circulation, and exposed or not exposed small body parts:

Small body parts, such as fingers, toes, ears, nose tips, and male genitals (sorry guys) have terrible mass-to-surface area ratios and shed heat like bajesus.

Fingers and toes have a built-in reflex to try and preserve them under harsh cold-weather conditions; This is definitely different in arctic-originating peoples, it could be reduced or different again in tropics-originating peoples but I'm not sure on that point.
On temperate peoples, the body first reacts to cold on the hands and feet (and cheeks) by dilating the little blood vessels in the extremities, rushing warm blood to the location to protect them from damage. As your body temperature drops, the body then contracts those little blood vessels, shutting off as much blood as possible and thereby restricting blood loss.
If you remain exposed, your hands/toes freeze and you get frostbite.

If you're from an arctic region (or probably other cold-adapted regions) the hands and feet then go through about 20 minute cycles of on-off-on-off to try and balance between heat loss and extremity loss, which helps prevent frostbite over long periods of hand exposure in the cold.

However, all extremities still have that terrible surface area problem. You can freeze these off before even getting chilled to the point of your body constricting bloodflow to extremities if the rate of heat loss exceeds the ability of your body to bring heat to the area via blood flow, even that increased flushing bloodflow. At -40(C or F, they cross around -42) with a breeze, you can most definitely have your ears or cheeks freeze before you even finish that initial flushing stage - your body simply cannot react fast enough to protect them. Add in some moisture - say, on your face from your eyes watering from a cold wind or from sun glare off snow and ice, or from sweat from being inside in heavy winter clothing - and it can happen VERY fast - even with your core well protected and no significant temperature drop or the faintest risk of hypothermia.

Regarding not defrosting frozen tissue rapidly - thats EXPLICITLY because the damage was caused by freezing. Frozen tissue is already fubar. It's frozen. Nearly cell has been ruptured by tiny spiky ice crystals, that tissue is dead dead dead and it's not going to get restored to life by warming it up (slowly or rapidly). People often have this weird idea that frozen = suspended animation, or that there's some sort of "5 second rule" with freezing. Humans are not filled with antifreeze; frozen icy = very dead. People pulled out from under the ice and revived aren't stiff ice-cubes, but I suspect people tend to visualize them as being corpsicles.

You defrost frostbitten areas slowly so as to not flood your body with that rather dead detritus of exploded cells faster than your body can cope with it. Otherwise you risk overloading the kidneys, and potentially adding kidney damage or total failure to the patients list of woes. Defrosting slowly allows the body's natural cleanup squad to try a sort of "calm and orderly" cleanup of the leaking goop and dead cells.

I seem to recall there's also a risk of the body seeing the sudden appearance of exploded cell contents as a major immune crisis, provoking extra inflammation - but it's past midnight here so I might be thinking of something else.



The difference between frostbite (restore to normal body temperature slowly) and burns (restore to normal body temperature quickly) is that the burn is on the surface, but the heat in the burnt tissue can keep radiating inward and basically slow-baking other tissue. Tissue on the inside has lost it's best route to dumping heat (those burnt outer layers) and need all the help it can get. Burns are usually fast.

Frostbite, on the other hand, is characteristically in superficial tissue - you can loose all your toes, but the bulk of your foot is much better protected by its mass and has a small contact area with those frozen toesicles. On top of that, the way your body warms up the foot to try to stop loosing it is by bringing in warm blood from elsewhere - not by trying to bring it in through the frozen region. So here, if you warm the core up, the patients body can prevent the freezing from progressing all on its own.

There's also the point that the temperature difference between burned flesh and normal body temperature tends to be more extreme than the temperature difference of frozen body parts to normal body temperature - excepting accidents with liquified gasses. Water freezes around +32F, and I doubt (excepting those accidents with gasses) people have managed frostbite down to temperatures much below -60F or -70F (in the antarctic with wet bits, up on Everest, that sort of thing). That's a differential of at most 170F degrees from normal; burns can go easily up to 500F or more, although 500F is carbonizing, so that's a hella horrible burn.

[Edris]

Originally Posted by bruno

Regarding not defrosting frozen tissue rapidly - thats EXPLICITLY because the damage was caused by freezing. Frozen tissue is already fubar. It's frozen. Nearly cell has been ruptured by tiny spiky ice crystals, that tissue is dead dead dead and it's not going to get restored to life by warming it up (slowly or rapidly). People often have this weird idea that frozen = suspended animation, or that there's some sort of "5 second rule" with freezing. Humans are not filled with antifreeze; frozen icy = very dead. People pulled out from under the ice and revived aren't stiff ice-cubes, but I suspect people tend to visualize them as being corpsicles.

You defrost frostbitten areas slowly so as to not flood your body with that rather dead detritus of exploded cells faster than your body can cope with it. Otherwise you risk overloading the kidneys, and potentially adding kidney damage or total failure to the patients list of woes. Defrosting slowly allows the body's natural cleanup squad to try a sort of "calm and orderly" cleanup of the leaking goop and dead cells

Actually, when treating frostbite/hypothermia the idea is to heat them up as quickly as possible normal core temperature without overshooting it. Some treatment plans place the target core temp as 95F, and move on to passive heating from there. The longer you leave the person frostbitten and hypothermic, the longer the consequences of hypothermic induced peripheral vasoconstriction will have to cause damage to the tissues. Some studies suggest that to improve neurological outcomes you actually keep the patient hypothermic for a period of time, copying induced hypothermia practices after cardiac arrest. One of the quickest ways to rewarm someone is with a cardiopulmonary bypass, allowing for up to 3.6F of core temperature rise per 3 minutes, for instance.

Some caregivers have noted that so-called "afterdrop" is negligible to overall patient recovery. The primary concern is actually cold acidotic blood returning to the body in afterdrop, not dead tissue cleanup. Dealing with gangrene/sepsis/necrotizing fasciitis is a result of infection a complication of, but not merely, dead tissue.

Originally Posted by Bruno

Frostbite, on the other hand, is characteristically in superficial tissue - you can loose all your toes, but the bulk of your foot is much better protected by its mass and has a small contact area with those frozen toesicles. On top of that, the way your body warms up the foot to try to stop loosing it is by bringing in warm blood from elsewhere - not by trying to bring it in through the frozen region. So here, if you warm the core up, the patients body can prevent the freezing from progressing all on its own.

That.. doesn't make any sense. Superficial tissue is the outer layer of skin, the epidermis, it doesn't have anything to do with toes vs feet. Frostbite uses burn stages used burn treatment (Stage I-IV) due to the similarities burns and frostbite present in tissue damage, the difference is just in initial treatment. It's true that frostbite is often characterized by toe/finger/ear/nose/cheek damage, but there's no reason it can't spread deeper to your feet or hands. Your body definitely prioritizes the core temp over the temperature of extremities. Typically, extreme hypothermic vasoconstriction in the extremities occurs below 95.9F core temp because of the release of norepinephrine. Your logic of warming the core up and the body preventing complications from freezing from progression is precisely the reason you want to warm people up quickly, actually.


If you'd like to share any studies that indicate otherwise, feel free, but the information in this post in particular is gleaned from continuing education articles for nurses from Lippincott/Wolters Kluwer.