| 摘要 |
PROBLEM TO BE SOLVED: To accurately measure gas of low concentration existing in environment by attaching and detaching and detaching a detection sheet that react to gas to be inspected being sucked by a gas suction means for generating color reaction to and from a measurement head. SOLUTION: In a window 3 being continuously closed by a cover 2 being biased by a spring 16, a measurement head 9 is arranged. The measurement head 9 is provided with a taper part 8 on an exposure surface from the window 3, and a measurement chamber 10 with a circular section being open to atmosphere is placed at the center part. In the measurement chamber 10, a gas inflow port 11 being connected to a gas intake port 7, and a discharge port 13 being connected to a suction pump 12 are provided. Also, a light emission means 14 for applying light to an opening 10a of the measurement chamber 10, and a light reception means 15 for receiving reflected light from a detection unit 20 are accommodated. During a measurement period, while a detection sheet 22 is shielded from external light by the cover 2, and at the same time is brought into contact with forced flow from the gas suction means for generating color reaction according to the concentration of the gas to be inspected for a short time while an airtight property is maintained.
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