When adsorbed gas is analyzed after metal, ceramics or metallic salt has been left in an environmental atmosphere for a predetermined period of time, an average concentration of specific gas over a long period of time can be accurately measured with an inexpensive small apparatus. Especially, porous metal or ceramics (transition metal oxide) are excellent in selective adsorption properties for NO.sub.x, porous ceramics (rare earth element oxide) are excellent in selective adsorption properties for CO.sub.2, and a specific chloride such as copper chloride and silver chloride is excellent in selective adsorption properties for SO.sub.2. A test kit accommodating such test pieces in a case, a protective case for the test kit to put the test kit into practical use, an umbrella and a forced air blowing unit are also disclosed.