Gas detection tubes operate in the following manner: An air sample is drawn through a tube containing a reagent, causing a color change. The concentration is then read from the length of the color stain in the reagent. The advantages of detection tubes over other analytical methods are simplicity of use, rapid response, low cost, and very low maintenance. Because each batch of Honeywell tubes is pre-calibrated, no calibration equipment is necessary. Errors are prevented by directly marking the calibration information on each tube, and accuracy is further ensured by controlling the volume of air sampled. Honeywell tubes are primarily of the narrow bore type and are designed for use with a Honeywell handoperated piston pump.