If it has, it doesn't. Those who are light and urgent, they are not.
Life blanket is an international universal, life-saving necessity, only the size of the palm after folding, can effectively reduce the body temperature loss, its use in danger.
First aid blanket to prevent body temperature loss - The aluminum film material of the life blanket is a highly reflective material that can disperse the human body
Reflect back with thermal radiation, so that even if it is effective, lower a certain height.
Three days, and so on.
Don't ignore this inconspicuous little object, otherwise the risk of not being warm will rise in the cold night in distress.