A carbon-monoxide (630080) (CO) dosimeter was evaluated for monitoring worker exposure. The dosimeter consisted of an Accuhaler and a Drager long term tube. Tests were run at high and low humidities, high and low temperatures, and high, low, or varying CO concentrations. High temperatures and high humidity affected the accuracy of the dosimeter. Other chemicals such as petroleum vapors, benzene (71432), and hydrogen-sulfide (7783064) did not interfere with the test, but acetylene, (74862) in amounts over 20 milligrams of water per liter, did interfere. Accurate responses were obtained for CO concentrations up to 600 parts per million.