NOVELTY - The fuel cell apparatus has gas detection sensor (34) for detecting the concentration of gas inside the fuel cell package (33). A ventilation opening (50) is closed by using an obstruction board (51), when the concentration of gas inside the package is more than predetermined concentration. The gas is kept from leaking towards the exterior of the package and the drive of the apparatus is stopped temporarily, until the concentration of gas is less than the predetermined concentration.    USE - Fuel cell apparatus e.g. solid polymer type fuel cell apparatus. Can also be used in molten carbonate type fuel cell apparatus and solid oxide type fuel cell apparatus.    ADVANTAGE - The leakage of gas in large quantities towards the exterior of package is prevented. A compact package is realized by arranging the water tank and heat radiating fin in the external reservoir tank. The warm liquid can be cooled efficiently by circulating the liquid inside the heat radiating fin and by sending wind through air blower. The heat radiating efficiency is improved since the influence of convection from water tank on the heat radiating fin is prevented by arranging the heat radiating fin in the lower part of the water tank. The installation can be performed easily by connecting the reservoir tank and package by using a piping. The fall of heat radiation effect due to penetration of foreign material, is prevented without the need for filter, the gas is prevented from exhausting in the form of white smoke and the adherence of water droplets in the exit portion of the package is prevented, by the provision opening and closing mechanism in inlet port and exhaust port in the housing. The apparatus is safely protected by the provision of earthquake sensitive apparatus. The user is notified about the vibration or external force quickly by the provision of alert light or sound. The stoppage of fuel gas from main fuel line can be detected directly and reliably by the provision of interruption detector.    DESCRIPTION OF DRAWING(S) - The drawing shows a longitudinal cross-sectional view of the fuel cell apparatus. (Drawing includes non-English language text)    Fuel cell (7)    Fuel cell package (33)    Gas detection sensor (34)    Ventilation opening (50)    Obstruction board (51)