Evaluation of passive card monitors for hydrogen sulfide for use in kraft pulp mill workplace atmospheres

Six different brands of passive card monitors representing three different types of card monitor were evaluated for their effectiveness in testing for hydrogen sulfide in workplace atmospheres. The cards were evaluated both in the laboratory and in a kraft pulp mill according to a protocol that closely follows that recommended by the National Institute for Occupational Safety and Health and other researchers for passive samplers. The performances of the Envirometrics Air-Chem Technologies and the Gilian ChemAir quantitative cards, the Gilian ChromAir and VICI Metronics Colortec semiquantitative cards, and the American Gas & Chemical Co. Leak-Tec and Gilian SafeAir indicator cards were evaluated. The detection limits of the cards were determined, and the cards were exposed to a range of hydrogen sulfide concentrations (1, 5, 10, 20 ppm), face velocities (0, 50 ft/min), and temperature/humidity combinations (95 degrees F/90% humidity, 77 degrees F/50% humidity, 40 degrees F/20% humidity). The cards' responses to short-term and variable concentration exposures as well as to the potential interferents methyl mercaptan, dimethyl sulfide, dimethyl disulfide, sulfur dioxide, and carbon monoxide were assessed. Each of the cards tested demonstrated a usefulness for the detection and/or quantification of hydrogen sulfide at concentrations and under conditions relevant to kraft pulp mill workplace atmospheres. Which card is best depends on the application, sampling conditions, and level of confidence necessary in the results. The Gilian ChemAir quantitative card performed well under most conditions with acceptable accuracy (13% lab, 26% field), and no response to potential interferents or to changes in face velocity, temperature, and humidity. The Envirometrics ACT quantitative cards did not perform as well, with an accuracy level of only 46% in the lab. They also seemed to be more affected by changes in face velocity, temperature, and humidity. Both semiquantitative cards (Gillian ChromAir, VICI Metronics Colortec) provided reasonable approximations of hydrogen sulfide levels in the range of the hydrogen sulfide occupational exposure levels although the VICI card had a much lower detection limit. Neither performed well at high temperature and humidity. The response of VICI card was more affected by changes in face velocity, whereas the Gilian ChromAir showed some response to reduced sulfur gas interferents. Both indicator cards (Leak-Tec, Gilian SafeAir) performed well, responding to 20 ppm hydrogen sulfide within 1 min and to 5 ppm within 5 min. Neither was significantly affected by extremes of temperature and humidity.