Features Research & Innovation
CO MUST BE MONITORED

VANCOUVER, BC — The Forest Industry Health Research Program (FIHRP) has completed a study of sources and concentrations of carbon monoxide (CO) in mill working areas. Sixty-nine sites at four BC pulp mills were surveyed in 1999 for CO emissions. The study focused on processes using oxidizing agents such as chlorine dioxide, oxygen delignification and peroxide delignification blow tube. One mill carried out a comprehensive survey of processes involving oxidative reactions. Relatively high peak and average CO concentrations were measured at some sites. None of the measurements exceeded the WCB exposure limits of 25 or 12.5 ppm averaged over an eight-hour or 12-hour shift, respectively, or 100 ppm averaged over 15 minutes. The highest average concentration was 11 ppm at the top of a peroxide bleaching tower. The highest peak value was 81 ppm at an O2 delignification blow tube. However, the average concentration at this site was only 1 ppm and the maximum 15-minute value was 12 ppm. Feed lines for peroxide bleaching and O2 delignification in basements gave average concentrations of 4 to 6 ppm. On the operating floor, CO levels at washer hoods after ClO2 or O2 averaged 2 ppm with little variation in the concentration. The bleach blend tank was identified at one mill as a source of CO into an indoor area. Concentrations of 50 to 60 ppm were measured in the vent gases. At 3 m from the vent, the CP level was 3 ppm, indicating a rapid dispersion of the gases. During one shutdown, CO concentrations of up to 64 ppm were measured inside a decker hood. This illustrates the importance of measuring CO before workers enter confined or enclosed areas. The report, Carbon monoxide emissions from pulping processes is available from the Pulp and Paper Employee Relations Forum; tel: 604-777-1533; fax: 604-777-1567; e-mail: alee@paperforum.com. Non-members of the Forum may be charged for the report.