A space blanket is an extremely slim plastic sheet coated with an ultra thin layer of aluminum which reflects body heat back onto a person who is cold. Added to emergency medical kits and carried by backpackers because of its incredibly compacted and lightweight properties, the space blanket can be used in a variety of ways. The original space blanket is fairly cheap, but newer, thicker versions can cost four to ten times more than the original blanket, and are available for camping, hunting, and extreme mountain climbing. Space blankets are also sometimes referred to as solar blankets, emergency blankets, Mylar® blankets, and a sleeping bag version of the space blanket is known as a bivy sac.
When used as a blanket to keep someone warm, the space blanket should be placed on top of a cloth blanket, if available, with the reflective surface facing up. The user should sit down on the blanket with their legs extended, fold the foot end of the blanket up over the feet, then lay down and wrap the sides around the body. If the space blanket is not big enough, a second space blanket can be wrapped around the top portion of the body, leaving a space for breathing. The cloth blanket can then be wrapped up around the space blankets. This blanket technology works by reflecting the body heat and warming a small pocket of air between the person and the emergency blanket, so the blanket should not be wrap tightly but should instead be gathered loosely around the person.
There are a variety of emergency uses of the space blanket. An emergency shelter can be built from the blanket by using it as a tarp or constructing it into a crude tent. The reflecting properties of the blanket can be used to intensely warm several people when the blanket is placed as a backdrop behind a group of people sitting in front of a fire, or the blanket can be used as a large mirror to signal for help. Emergency blankets can even be used to keep people cool when the reflective side is turned up and the blanket is used for shade.
Many non-emergency uses exist for the blanket as well. Hospitals will sometimes use space blankets during surgery to combat the chills which sometimes accompany the use of anesthesia. Long distance runners are often wrapped in space blankets at the end of a race to prevent sudden loss of body heat.