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Abstract
A device has been developed by researchers at the National Institute for Occupational Safety and Health (NIOSH) for real-time monitoring of exposure to airborne contaminants, including in-mask respirator sampling. The device consists of a small breathing-zone sensor connected to a belt-mounted unit. The cylindrical sensor, which weighs 15 g and is 2 cm in diameter and 2.5 cm long, contains a thin film of chemical reagent that changes color upon exposure to a particular contaminant, and an optical system that monitors the color change. The belt-mounted unit (450 grams) provides power to the sensor, pulls air through it, and processes its electrical output. The output signal is a function of the total contaminant exposure, can be processed to provide real-time concentration data, can be recorded, or can be used to trigger an audible alarm. Five prototype devices were constructed and their capability to monitor ammonia and mercury was investigated. Evaluation of this device using a commercially-procured reagent film for ammonia, indicated good correlation for response of individual units as a function of dose and for interunit and intraunit response (R 2 = 0.99). However, evaluation with a reagent film for mercury vapor manufactured in-house produced varying results depending on the film's conditioning prior to use. Currently, the techniques for monitoring personal exposure to these contaninants are limited to conventional environmental sampling and analytical techniques which require laboratory analysis (producing only time-weighted average measurements) or instrumental techniques which provide a real-time determination of concentration, but seldom allow the determination of analyte in as workers breathing zone. From the present research, it was concluded that, when the proper film is available, this device provides a convenient method for accurate, real-time measurement of a contaminant at levels near the applicable environmental criteria. Therefore, the advancement of this monitoring technique will depend on the reliable production of suitable films based on the many colorimetric reactions already known.