Glass detector tubes are filled with an inert reagent carrier material (silica gel, aluminum oxide, or aluminum silicate) impregnated with an indicating reagent. Reagent produces a colorimetric indication in the presence of a particular gas, vapor, or aerosol. Concentrations can be read directly from the color change on the tube's printed scale. Tubes are hermetically sealed. Most have a two-year shelf life (when stored at room temperature). Available in packs of ten.
Note: Some tests require a pretube or comparison tube in addition to the detector tube. These tubes are included in the box of 10, thus reducing the number of detector tubes. The actual number of detector tubes is cited in the ordering charts.