The transportable device has container (1) to receive foodstuff (8), and heating chamber (2) which adjoins container while simultaneously being hermetically separated by thermally-conductive wall (4). The heating chamber has chambers (5,6) that are separated by water vapor-permeable wall (7). A substance/substance mixture (9) in chamber (5) generates heat in exothermic chemical reaction to form water vapor, when liquid such as water is supplied. A zeolite (10) in chamber (6) adsorbs water entering from chamber (5) via water vapor-permeable wall by generating heat.
