To stabilize a gas substittution speed by providing a replenishing tank for replenishing a reducing agent at the upper part of a reducing cylinder that is filled with the reducing agent and allowing a sample gas that is introduced from a gas entrance to contact the reducing agent in the replenishing tank.
Active carbon 2a is put into a cylindrical part 7 of a reducing cylinder 1, and a gas entrance 4 and a gas exit 5 are provided at the top of a conical part 9. An insertion pipe 14 of a replenishing tank 12 for replenishing an active carbon 2b into the reducing cylinder 1 is provided while it projects downward from the lowest position of an inclined bottom surface (n) and an upper lid 16 covers an opening 15 for replenishment being formed on an upper surface (e). The insertion pipe 14 is inserted into an insertion hole 8a of the conical part 8, an opening (m) is connected from the center of an upper net 11 to a cut-out 11a at a position deviating from the center of the upper net 11 and a replenishment tank 12 is installed, and the active carbon 2b is brought into contact with one portion of a sample gas S in the reducing cylinder 1. Although the active carbon 2a in the reducing cylinder 1 is consumed due to a reduction reaction, the active carbon 2b is repeatedly supplied from the replenishing tank 12 by the amount of consumption each time, thus increasing a gas substitution speed.
EKUSA TAKASHI
INAI MINORU
KUSAKA TAKESHI
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