The downfall of these emergency blankets for shelter co […]
The downfall of these emergency blankets for shelter construction lies in their lack of strength once punctured, and because of Aluminum mylar that lack of strength, their utility in the rough reality of outdoor environments suffers as well. Once anything pokes through the material it tends to rip apart very easily from that point, leaving the survivor with uneven, and small, resulting pieces every time something pokes a hole in the blanket. Things like, stickers, thorns, sharp twigs, broken branches, rough bark, rocks etc. all provide ample opportunity to accidentally puncture the blanket and ruin its integrity.These inexpensive emergency blankets usually consist of a plastic material called oriented polyethylene terephthalate. In manufacturing, the BoPET material is combined with a microscopically thin layer of metal often aluminum sprayed on the plastic to give the heat reflective properties these blankets are famous for.
The most well-known brand name for this BoPET material is Mylar, which makes up many of the inexpensive emergency blankets already mentioned above. These emergency blankets work extremely well for specific applications. For example, using one as a vapor barrier and thermal barrier inside of traditional blankets and other insulation while transporting a patient in a liter. The Mylar material provides almost no insulation, instead it reflects radiated heat infra-red radiation, presumably back to the survivor. Be careful, this means laying a space blanket on the ground and then lying on top of it will not prevent any conductive heat loss direct contact to the ground.
Similarly, a sheet of plastic provides very little protection from heat loss through direct contact as well.When the situation dictates the need for immediate action shelter, a survivor attempting to use a Mylar blanket will quickly discover the many downfalls of the material. Firstly, the light-weight nature of most emergency blanket prevents the user from simply draping it over themselves like a blanket on a bed. In such a case, any movement or even a puff of wind will displace it, allowing any trapped heat to escape. Next, the rectangular shape means our survivor needs to wrap it around their torso, head and neck and hold it together under their chin.
This does provide some wind and rain protection, but this configuration leaves the bottom of the blanket open around the legs and also allows the reflected heat to escape. It also means that if our survivor falls asleep, the blanket will fall open. In addition, the material makes a tremendous amount of noise when anywhere near the ears. It crinkles loudly when the wind blows, or when it moves at all. The noise potentially covers up the sound of rescue, passing aircraft, or even voices in the distance. Finally, the reflective surfaces reflect the surroundings, potentially making the survivor even more difficult to see given the right conditions.If you like Mylar’s properties, look for it bonded or stitched to something stronger and brightly colored. Several manufacturers offer Mylar lined plastic bags emergency bivy sacks and even heavy-duty insulating blankets or tarps with a Mylar layer stitched to the other materials.