text: Together with 1,3,5-trioxane, hexamethylenetetramine is a component of hexamine fuel tablets used by campers, hobbyists, the military and relief organizations for heating camping food or military rations.  It burns smokelessly, has a high energy density of 30.0 megajoules per kilogram (MJ/kg), does not liquify while burning, and leaves no ashes, although its fumes are toxic.
  Standardized 0.149 g tablets of methenamine (hexamine) are used by fire-protection laboratories as a clean and reproducible fire source to test the flammability of carpets and rugs.