NASA developed Mylar blankets for use in the Apollo program, but reflective insulation existed for decades before that. Mylar blankets can reflect up to 90% of body heat back to the wearer.
How Do Mylar Blankets Work
Normal insulation traps air in little pockets and stops warm air from moving away from the skin. This means that thicker insulation works better than thinner insulation, so how can Mylar blankets work so well as insulation? Mylar blankets are reflective insulation; it works by reflecting radiant heat back towards the source.
Most of the heat the body loses is radiant heat, so reflective insulation makes sense from a heat loss perspective. It also makes sense because reflective insulation doesn’t have to be thick in order to work; it just has to be shiny and reflective.
In fact, the shinier the material, the better it is at reflecting heat, so if Mylar blankets get dirty they won’t insulate as well.
Mylar Blankets in First Aid
Keeping warm is a good idea in most cases, but during emergencies that involve major blood loss, winter temperatures, and/or water, it is especially crucial.
Obviously, low temperatures can cause hypothermia if a person is exposed for too long, but some of the real dangers occur when water and blood loss are involved. Water conducts heat much faster than air, and if the person is wet out of the water, evaporative cooling can suck up even more heat, especially if it is windy.
Although many people do not associate blood loss with heat loss as often as cold water or winter temperatures, it is one of the most dangerous causes of hypothermia. Your body uses blood to control the heat distribution in your body.
By dilating and constricting blood vessels near your skin, your body regulates its core temperature . When you lose a lot of blood your body cannot regulate temperature as effectively, and all of that warm, lost blood is lost heat as well. Even if it is warm outside, ALWAYS cover blood loss victims with blankets if possible. Hypothermia is an all too common secondary problem.
Blizzard EMS Trauma Blanket by PerSys Medical
DISCLAIMER: I received a free sample of this product in exchange for my honest, unbiased review.
From the makers of the Israeli Bandage, the Blizzard EMS Trauma Blanket is exactly what it sounds like. It keeps you warm in an emergency when it is cold, but what makes it different from a regular mylar blanket?
Both regular mylar and the Blizzard EMS Blanket use reflective insulation for heat conservation. In fact, the Blizzard EMS Blanket uses 2 layers of mylar to combat one of the problems of mylar. As I mentioned before, if your skin is touching the blanket, it won't work because the blanket will conduct your body heat instead of reflecting it back at you.
The Blizzard EMS Blanket uses 2 layers of mylar glued into tubes that trap heated air and prevent it from escaping. It also has elastic lines wrapped in horizontal bands, threaded through the tubes that keep the tube sides from collapsing and touching each other. This means that even if your skin is touching the inner layer of the blanket, the reflective insulation is still working.
The one caveat to this is lying on the ground. If you are lying on the ground, reflective insulation will not do much to hold your heat. It will keep you dry, but that is about all. The ground absorbs body heat faster than air, so having a pad or some other solid insulation between you and the ground is important, even with this blanket.
It has a good length to it, even for tall people. I am 6 ft tall, and I can easily wrap my feet in the end and cover my head at the same time. It has a thoughtful design that works well to conserve heat. I was surprised by the elastic bands, but they really seem to do their job keeping the tubes open and working to conserve heat. This blanket definitely retains heat better than a single mylar blaket, and it is sturdy enough that it earns the reusable tag on it.
The closure tape works well even if it takes a bit of time to do up the front, and if you open it back up, it actually even works good for a second stick as long as you keep it clean.
Of course this is larger and more expensive than a mylar blanket, and of course this is not a full solution for heat retention while sleeping on the ground. I don't really consider these cons because it is implied in the design. For me the biggest problems are the lack of O-rings and the absence of draw strings at the ends.
- O-rings in the corners are a small addition to the design that wouldn't take up more space, and they would make it so much more versatile. With a few ropes, you could use it to reflect fire heat, as a makeshift shelter, or adapt it to any situation that needs a waterproof tarp/heat reflector. No O-rings severely limits this product's adaptability.
- As a hammock camper, one of the problems I find with being suspended in the air overnight is that I crush my sleeping bag's insulation against the hammock, and my back gets freezing. To prevent this, I sometimes sleep with a pad in the hammock, but that's kind of bulky. The Blizzard EMS Blanket could slip right over the entire hammock. It would eliminate heat lost from crushing the insulation between you and the ground. With drawstrings, you could cinch the ends closed around the ends of the hammock to hold heat.
- Do not press the Mylar blanket right against the skin. This will transfer your body heat through conductivity instead of radiation. Mylar blankets only reflect radiated heat. Leave some air space by putting on a jacket or normal blanket underneath the Mylar.