Laboratory Evaluation of Passive Colorimetric Dosimeter Tubes for Carbon Monoxide

Abstract The recently developed passive colorimetric dosimeter tubes potentially offer great advantages of compactness, convenience, and simplicity in environmental evaluation of a wide variety of toxic gases and vapors. These devices do not require pumps but operate on diffusion principles to produce stain lengths proportional to time-weighted average concentrations that can be read immediately at the site. The purpose of this study was to evaluate the performance of colorimetric passive dosimeter tubes for carbon monoxide under dry and humid conditions. A flow dilution system using 2.58 percent carbon monoxide in air from a cylinder was used to provide 25, 50, 100, and 400 ppm of carbon monoxide at relative humidities of 20 percent and 82 percent and at a temperature of 26°C. Tubes from three manufacturers (Gastec/Sensidyne, Draeger, and MSA) were exposed for periods up to six hours, and the stain lengths were read (independently) by two observers at quarter- and half-hour intervals, depending upon the ...