On paper and for demonstration purposes, firebeds look good. The problem is when you really need one, the firbed will be made under less then idea conditions and materials. These factors may mean that the firebed though dug down and covered still emit smoke and gas from the wood smoldering. Trying to sleep on top of this with your lungs and eyes burning from the smoke and gas makes for a real sleepless night....There are much better ways of keeping warm with fire then this method.