A study in the current issue of Annals of Work Exposures and Health notes that the worldwide wood pellet market has grown rapidly. Growth rates have been about 10% annually from approximately 19.5 million metric tons in 2012 to approximately 28 million metric tons in 2015. In 2016, the demand for industrial wood pellets was estimated to be approximately 13.8 million metric tons.
However, most of the pellets used for residential heating (US measures) are sold in 40-pound (18.1 kg) plastic bags. The study measured carbon monoxide (CO) emission factors from fresh, bagged-wood pellets as a function of temperature and relative humidity. CO concentrations increased with increasing temperature and moisture in the container. CO measurements in a pellet mill warehouse with stored pallets of bagged pellets had eight-hour average CO concentrations up to 100 ppm exceeding occupational standards for worker exposure. Thus, the authors conclude that manufacturers, distributors, and home owners should be aware of the potential for CO in storage areas and design facilities with appropriate ventilation and CO sensors.
A full report on ‘Carbon Monoxide Off-Gassing From Bags of Wood Pellets’ has been published by Oxford University Press (OUP).