Are the foil bags really that bad? I have just ordered one today to replace my orange bag, which I find to heavy and bulky, but I'm wondering if I should have stuck with it now as the foil bags can tear??
i always carry a orange survival bag and whistle, and again a survival blanket
if the worsst should happen i can get in my surival bag and wrapp the blanket roung me if needed, or the same works if its used on another person
ive always been told to cut a hole at the other end and put your head throught, this is because you dont want you head in the bit with a big whole and allowing water to get in as much , anyone else herd this ?
Every year the Scottish Mountaineering Club publish a list of accidents in the mountains. The SMC Journal 2000 reports that on February 15/16 at 16.00 a couple got lost at the top of Aladdin's Couloir in the Cairngorms and got into bivi bags near the head of Coire Raibert. The Mountain Rescue Team found the couple the next day at 11.15. An extract from their report reads: The woman "was in a Goretex bivvy bag and recovered quickly ... The man was severely hypothermic, poorly equipped in an orange plastic bag, frozen to the ground, his face a mask of ice.... Patient declared dead".
Can there be a clearer, or more tragic, example of the difference between a good bivvy bag and an orange plastic one?
yes there can, and it has been documented for over 150 years. there are differences between men and women in cold conditions. enough said. if your still not sure, check out the "dalton party", this is the most famous/gruesome example of female survival in cold conditions.
Comparative merits of dirrerent survival bags and shelters would be an interesting topic for someone to research. I believe there have been other cases of people getting hypothermic despite being in an orange plastic bag, but I would think there are a lot of contributory factors, like their clothing, general fitness, how wet they were and what state they were in when they stopped to take shelter. In severe conditions it's better to share a bag if possible and for that reason I sometimes carry a double sized orange plastic bag in winter conditions.
good question G-Ject. I personally dont want to have any any weight, but just accept that some things have to be carried "just in case". the whole issue of what kit is carried in remote or mountain area's is an interesting one, and can be viewed in many ways. e.g. how many walkers perceive that they should only carry a minimal first aid kit on a one day walk, but a bigger one on a longer walk?. Surely only the quantity of items should change, and not the variety.once walkers think about this, it often becomes clear that long accepted rules are total folly. So back to earlier post's, and how much extra weight will we accept. As for me I carry a foil blanket in my first aid kit, for normal day to day accidents (car crash, sitting wounded) and have two plastic survival bags, one thick and one thin, only using the thick one if i am going somewhere rocky. I like most others, stick it in the bottom of my pack, which in the event of serious injury might make it virtually impossible to get back out!, but then that leads us back to pre-conceived idea's, I.E., will it actually be me or some passer by that puts me in the bag, or uses my first aid kit.
Sorry to post back to back, but for any of you folks that has watched a first aid training film, have you ever noticed how the victim is treated by someone else, and not themselves! (minor cuts excepted), try to think of your first aid kit, as a kit for someone to use on you, as well as YOU on OTHERS. Sorry for the rant, rant mode over now, and yes its not really survival bags, but it is linked to their use.
I've always had one of those organge plastic sacks since it was drilled into me at school that we should carry one. I've used it for sledging, sitting on, wrapping stuff up, but mostly as a tent groundsheet. Obviously, I've worn them out and replaced them over the years. There was a spell of several years when I bivvied quite a lot using one, but my preferred method was simply to use it as a groundsheet, pop the sleeping bag on top, and sleep under the stars, even to the extent of bivvying on top of Bidean nam Bian. British weather often cut my sleeping time short, and if it's one thing I learned to detest, it was sleeping INSIDE one of those bivvy bags in the rain. Pure misery! Still, I rate them as better than nothing for emergency shelter, but you'd be a lot better off inside a sleeping bag in a tent any day. As I've just bought a polycro groundsheet to plonk my tent on, I may well retire my current orange bivvy bag and save another 100g or so.
I carry an orange poly bag and a reflective blanket whenever I am on the hill. My reasoning is as follows (apologies for the geeky response, but I am a physicist/engineer)...
Poly bag - modest insulation against conductive heatloss (so good if you are forced to lie on wet ground) plus wind and rain resistant to help prevent heatloss from damp clothing and windchill. Highly visible and fairly robust.
"Space blanket" - cuts radiant heatloss dramatically. As mentioned, fairly useless in windy conditions but if practically possible I would wrap my body core up in one, including covering head and put my insulation & shell layer on over the top. This would have several benefits (in theory at least).
Firstly, presuming my baselayers/ midlayers weren't too wet to start with, it can be a good idea in a survival situation to limit the rate at which sweat can evaporate from the body. Trapping some humidity close to the body may feel damp but in the short term would actually keep you warmer by reducing the rate of evaporative heatloss ( vapour barriers are often used inside sleeping bags in the coldest conditions for this reason). It could also slow dehydration and help keep insulating layers dry (hence warm) inside that poly bag.
Secondly, radiant heat loss from a hot body to a cold environment is dependent on the emissivity of the surface (roughly the opposite of reflectivity). The foil blanket has a very low emissivity so most (I have read 80%) of the radiant heat is reflected back to the wearer. The poly bag will do very little to cut radiant heat loss.
As I say, that's my theory but thankfully I have never had to test it!
I used to carry an old tent flysheet...waste not want not, and all that. I've looked a few times at the Vango storm shelters...anyone used those, and if so, are they any good? I've never had to bivvy in the flysheet, but it did save me from a severe hail-pounding once.
I've carried one of blizzard bags since they came about. Still vacuum packed but very small. When going with a few people I carry a group shelter (bit heavier) but only when going to some serious ground and well away from the likelyhood of a quick rescue if it all goes wrong.
This is what people used to do before the bothy bag (or kisu or group shelter) was "invented" and in my experience they work just as well and in much the same way.
I thought vapour barriers were used in very high end sleeping bags to prevent perspiration and moisture on your clothing reducing the effectiveness of the down insulation dramatically. Once the perspiration has been evaporated from the skin surface it is then permeating its way through your clothing. As it condenses it does give up its latent heat, but it is leaving a moisture content in your clothing reducing its effectiveness. This may explain in some instances where you might be better off in a gore-tex or event bivi bag rather than a poly bag as you stay drier just the same as walking in a pvc jacket will leave you drenched in sweat and chilled.
I do believe radiation of heat is more important at higher temperatures than the body produces with convection being more important.
There are a few examples of aluminsed insulation such as some TNF garments which now use Primaloft. However the principle of insulation is to trap still air which is 30 times less conductive than water. Preventing convective currents is important as is shown comparing Exped down mats to normal air beds thermal properties.
There is kits of two poly bags with the principle that you pack the space between them with moss and branches etc as insulation and then get into the inner bag, obviously this is not much use on a barren hillside with a broken leg.
The blizzard bags have multiple layers which allow it to trap still air in a sleeping bag fashion although it shares the same problem that most insulation value is lost where it is compressed under body weight.
Perhaps more important than you realise would be your choice of insulation with buffalo products and synthetic insulation far more capable than down when wet.
yes - I agree that the jury is out on the benefit of vapour barriers, but there's an interesting if somewhat confusing article about them by a small (somewhat eccentric ?) US manufacturer :
http://www.warmlite.com/vb.htm
and a more general and clearer perspective on thermoregulation at
I am of the opinion that vapour barrier clothing would probably be one of the most effective ways of staying warm (not necessarily comfortable) but in normal active use would be extremely difficult to regulate. I have never tried it, but the theory seems reasonable.
Radiative transfer is a function of the fourth power of the absolute temperature (Stefan's law). That's just a fancy way of saying that it is much much more significant when there is a large difference in temperature between the hot body and the cold environment. Even in a relatively warm climate, heat loss can be significant via radiation especially if there is a clear night sky. At this point you (37 degrees) are radiating almost unhindered to deep space (-270 degrees... or 300 degree differential). Sitting under a tree (plants are good Infrared reflectors to avoid overheating during photosynthesis) and cloud cover can reduce this problem, but reflective materials could certainly help in my opinion, and weighing so little makes it academic.
Convection and evaporation are the most significant forms of heatloss while a walker is moving (conduction only really occurring through the feet) but conduction and radiation would become important when you are lying on the ground at night - i.e. a survival situation.
I wonder if anyone has seriously researched the relative merits or if it's all just traditional lore...
A pal of mine in the Army told me that in an emergency a couple of bin-bags are useful: one next to the skin to keep perspiration away from clothing, the other over everything to keep as dry as possible. I guess that's a kind of improvised vapour barrier strategy. It is imperative to keep insulating layers dry - as soon as they are wet they will conduct heat away fast.
