aggie79 wrote:Sounds like a recipe for death by carbon monoxide poisoning.
You have a point there. In fact, some of the early warnings said the healthy people do not need them, and the weak should use sand heated red-hot, to avoid the fumes. Normally, bed warmers were used like an iron, being passed back and forth between the sheets to take the chill off, not left in the bed.
When I was on winter operations, I would keep some of the instant hand warmers in my ruck. When we bivouacked, I would roll out my bag and throw 2 of them inside. After crawling in later, I would take them out and drop them in my boots. Warm sleeping bag at night, warm dry boots in the morning.