Making these and storing them to use if the power goes out, will probably, no, literally save your life. These can heat up a room, used to cook food on and best of all, hardly any smoke is produced, so could be used in a survival situation.
All you need is sawdust and paper… easily found for free. loose sawdust can be burned in a wood burner but can easily kill the fire and cause a lot of smoke. Learn how to make this and make a good stockpile for that “just in case” situation.