A CO monitor (Model ZDL-500, Environmental Sensors Co., USA) and a temperature (T)/RH (EL-USB-2+, EasyLog, LASCAR electronics, China) monitor were attached to the inside bottom of the cover ( Fig. Two sealed bags of pellets were inserted into each drum for each experiment. The 55-gallon drums were sealed by a metal ring to maintain an airtight fit against a gasket. (2015b) except using 55-gallon (208.2 l) carbon steel drums. The experiments were conducted in a manner similar to that described by Soto-Garcia et al. To ascertain if these emissions represented an occupational hazard, measurements were made in the warehouse of an active pellet mill. Wood type (hardwood, softwood, and blended) affects CO emissions ( Soto-Garcia et al., 2015b) and off-gassing from hardwood, softwood, and hardwood/softwood blended bagged pellets was measured. CO emissions from bagged pellets were studied as a function of temperature, and relative humidity (RH) that could mimic storage conditions in a warehouse, basement, or garage. The objective of this present study was to understand the impact of storing bagged pellets by manufacturers, distributers, and consumers by estimating the emission factors for CO off-gassing. ![]() Similar results have been obtained in other studies ( Kuang et al., 2008 Emhofer et al., 2014). (2015b) measured the emission factors for CO off-gassing from loose hardwood, softwood, and blended pellets by storing pellets in steel drums and measuring the resulting CO under varying temperature and moisture conditions. There is currently no published information regarding the off-gassing of CO from the stored bagged-wood pellets and the resulting impacts on air quality in occupational or residential spaces. The perforations of the plastic bags suggest that the CO generated from these pellets can emanate from the bags, enter the storage area, and result in exposures to building occupants. ![]() Pellet manufacturers and distributors generate or store large quantities of bagged pellets in warehouses for extended periods before selling them to the customers. The bags are perforated to allow for stacking on the pallets without the air in the bags inflating them and thereby preventing effective packing.Īfter purchasing bagged-wood pellets, consumers often store 1–3 tons of pellets in an inside storage room or in the basement until they are needed. To store and transport the bagged pellets, they are normally stacked on pallets with typically a ton per pallet. These studies were performed using bulk wood pellets, but most wood pellets in the United States are sold and distributed in plastic bags containing 10 to 25 kg ( Safe Pellets, 2012). (2017) measured CO concentrations in areas with indoor storage of bulk wood pellets in homes and reported that 6 of the 16 homes tested exceeded the 9-ppm American Society of Heating, Refrigerating and Air-Conditioning Engineers ( ASHRAE, 2009) guidance concentration on multiple occasions. (2015a) measured 8-h average CO concentrations up to 35 ppm in a residential basement. Fourteen fatal accidents have been reported since 2002 resulting from the storage or transport of bulk wood pellets ( Gauthier et al., 2012). However, a problem exists with respect to the safe handling of wood pellets and that is off-gassing of carbon monoxide (CO) and aldehydes into storage bins and shipping vessels ( Svedberg et al., 2004, 2008, 2009 Arshadi and Gref, 2005 Hagström et al., 2008 Kuang et al., 2008 Arshadi et al., 2009 Granström, 2010 Soto-Garcia et al., 2015a). In 2016, the demand for industrial wood pellets was estimated to be ~13.8 million metric tons ( WPAC, 2017). Growth rates have been about 10% annually from ~19.5 million metric tons in 2012 to ~28 million metric tons in 2015 ( WPAC, 2017). ![]() The worldwide wood pellet market has grown rapidly. Bagged-wood pellets, CO off-gassing, emission factors, exposure Introduction
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