GASTEC Color Dosimeter Tubes provide reliable, on-the-spot time-weighted average (TWA) monitoring of worker exposure to gases and vapors. Simple to use and easy to read, insert the tube into a tube holder and snap off the pre-scored end of the tube. Place the tube on a worker near the breathing zone, except when measuring carbon dioxide (see second Tech Tip below). No pump, chart, or analysis is needed. Read the printed calibrated scale on the tube for exposure measurement in parts-per-million-hours (ppm-hours). Divide the reading by hours sampled for ppm levels.
- When using passive color tubes, the time-weighted average can be calculated at any time during the measurement period by simply dividing the length of the tube reading (in ppm-hours) by the elapsed sampling time (in hours).
- To avoid overstating carbon dioxide levels because of exhalation, place passive color tubes for carbon dioxide at the waist instead of the normal position in the breathing zone.