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.
- 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.