NOVELTY - The apparatus (1) has water supply apparatus (11) which is connected to siloxane decomposition catalyst (9). A gas supply apparatus supplies the gas containing siloxane to the siloxane decomposition catalyst. A gas pre-heater (12) heats the gas supplied to siloxane decomposition catalyst at hydrolysis reaction temperature. A cooler (13) cools the gas and collects the moisture content. A gas flow path of inflammable gas detector is provided in the upstream position.    USE - Siloxane decomposition apparatus for inflammable gas detector for combustible-gas control apparatus used in nuclear power generation system, digestive gas-engine electric power generation system, fuel cell power generation system, reclamation gas electric power generation system, and in semiconductor manufacture manufacturing plant (all claimed).    ADVANTAGE - The gas supply apparatus supplies the gas containing siloxane to siloxane decomposition catalyst, when siloxane is included in the system, so that fall of catalyst performance can be suppressed.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) inflammable gas detector which has sensor device of catalyzed combustion system. The combustible gas consists of hydrogen, carbon monoxide, methane, and hydrocarbons.;    (2) nuclear power generation system which has combustible-gas control apparatus, hydrogen detector or catalyst type hydrogen re-combiner;    (3) combustible-gas control apparatus for nuclear power generation system which has recombination catalyst in which the hydrogen is generated. The hydrogen is react with the oxygen in the inner side of combustible-gas control apparatus;    (4) digestive gas-engine electric power generation system;    (5) fuel cell power generation system;    (6) reclamation gas electric power generation system;    (7) semiconductor manufacture manufacturing plant which has clean room from which gas is passed to the siloxane decomposition apparatus; and    (8) operating method of siloxane decomposition apparatus which involves changing gas volume flows into catalyst layer temperature, when removal rate of siloxane is estimated to fall from target value.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the siloxane decomposition apparatus. (Drawing includes non-English language text)    Siloxane decomposition apparatus (1)    Siloxane decomposition catalyst (9)    Water supply apparatus (11)    Gas pre-heater (12)    Cooler (13)