Measurement of particulate matter emission rates from mechanically ventilated swine barns

Methods for measuring emission rates of particulate matter (PM) from mechanically ventilated livestock buildings were evaluated in the laboratory using a test chamber. Particulate matter concentrations were measured inside the chamber and at the exhaust duct. Concentrations at the exhaust duct were determined using high-volume traverse downstream of the exhaust fan, low-volume traverse downstream of the fan, and fixed sampling upstream and downstream of the fan. The high-volume traverse was the reference method. Both traverse methods were conducted under isokinetic conditions; fixed sampling was done under both isokinetic and sub-isokinetic conditions. Both room sampling and exhaust sampling under sub-isokinetic conditions severely overestimated exhaust PM concentrations. The low-volume traverse and fixed sampling under isokinetic conditions agreed well with the high-volume traverse (mean difference ranging from 7% to 14%). Methods involving room sampling, fixed sampling at exhaust, and high-volume traverse at exhaust were also compared in a swine finishing barn. Room sampling overestimated concentrations at the exhaust by an average of 30%, and PM concentration from fixed sampling did not differ significantly (p > 0.05) from that of the high-volume traverse method. It appears that fixed sampling under isokinetic conditions can be used as an alternative to the high-volume PM traverse method to accurately measure PM concentrations at the exhaust, from which the PM emission rate can be determined.