Effects of watering/steaming of large square hay bales on particulate matter generation

One of the factors strongly influencing air quality in horse stables is the release of airborne particulate matter (APM) from roughage. This study examined the effects of a new system of steaming whole hay bales on the release of APM from hay. The hay bales were first watered from above and then placed in a specially constructed box and steamed with water vapor. To determine the effect of steaming the bales on the release of APM <10 mm (PM 10) and <2.5 mm (PM 2.5), samples of untreated and treated (watered and steamed) hay were examined under standardized conditions using a gravimetric particle analyzer (TEOM 1400a). In addition, the moisture content of the samples was measured. The average moisture content of the untreated samples was 13%. After watering/steaming the average moisture content rose to 31%, with a gradient from the surface to the center of the bale. Compared to untreated hay, watering/ steaming of whole hay bales showed a nearly 90% decrease in PM 10 and PM 2.5 release and a mean decrease in bacteria and mold content in the hay dry matter (DM) of 49.70% and 34.53%, respectively. However, the quality of the watering/steaming process and hay bale texture has to be considered. Furthermore, an exponential relationship between the moisture content of the hay samples and their PM 10 and PM 2.5 release could be shown. A reduction in PM 10 and PM 2.5 release was determined for a moisture content of up to 25%.