Less hazardous methods for generating thermal energy for heating water, medical supplies or comestible products using improved flameless chemical heaters/flameless ration heaters by novel chemical or electrochemical means, each capable of suppressing the generation of hydrogen gas. Remote unit self-heating meals may be more rapidly heated by forming a reaction mixture comprising magnesium or a magnesium-containing alloy, and a hydrogen eliminator or suppressor, and introducing water to react the reaction mixture and generate a more rapid release of thermal energy sufficient to effectuate a more accelerated temperature rise and more rapid heating of medical supplies, water, rations or other comestible substances while simultaneously suppressing or eliminating the generation of potentially hazardous hydrogen.