This invention relates to a self-heating or self-cooling container (1), which uses an exothermic or endothermic reaction to provide or remove heat from the contents of the container. The chemical reaction includes a fluid consistuent (either as a reagent or solvent), held in a reservoir (6), which is added to another reagent in the reaction chamber (5) to initiate the reaction. The container (1) according to the invention proposes a means (8, 91) to control the volume of this fluid constituent added to the reaction chamber (5) depending on the ambient temperature of the container.
