Water Vapor-Ultra Low Range (2-12 lb/MMCF). Sensidyne gas detector tubes are made from high-quality borosilicate glass tubes with a uniform inside diameter. Inside, each tube is packed with a specific gas detecting reagent and available for the sampling of over 300 gases. When both ends of a detector tube are broken, inserted into the Model AP-20S Sensidyne Gas Aspirating Pump, and an air sample is pulled through the tube by means of pulling back on the pump handle, the detecting reagent changes color. The length of the discolored layer is proportional to the concentration of the gas or vapor in the sample because of the fixed volume of sample, which is always 100 ml. Graduations printed on the tube showing the gas concentration make it fast and easy to take a reading with Sensidyne detector tubes.
