PURPOSE: To maintain working environment in production of semiconductors by using activated carbon attached with sodium hydroxide or mercuric chloride.

CONSTITUTION: The activated carbon attached with the sodium hydroxide or mercuric chloride is used as a capturing material for analysis. While the activated carbon attached with the sodium hydroxide is suitable for capturing arsine and phosphine, the activated carbon attached with the mercuric chloride is suitable for capturing silane and germane. Diborane and hydrogen selenide can be sufficiently captured even if the capturing agent attached to the activated carbon is the sodium hydroxide or the mercuric chloride. The sodium hydroxide is attached to the activated carbon preferably at 0.5W2g per 10g activated carbon and the mercuric chloride is attached thereto preferably at 2W20mg per 10g activated carbon. The working environment in production of the semiconductors is thus maintained.