Hydrogen Sulfide Assessment in Shallow-Pit Swine Housing and Outside Manure Storage

摘要

In Saskatchewan, some recent incidents have lead its to believe that certain manure management activities can potentially release high concentrations of H_2S into the atmosphere of shallow-pit barns. The objectives of the monitoring project reported here were to evaluate worker exposure to H_2S during the completion of the following tasks: emptying of in-barn shallow manure pits, power washing of barn rooms, and agitation and emptying of outdoor manure storage facilities. In-barn monitoring was performed in gestation, farrowing, nursery, and grow-finish sections in the. summer of 2001 and the winter of 2002 on four different farms. Plug pulling can generate very high concentrations of H_2S. The maximum values recorded during some of the monitored events reached 1,000 ppm. The H_2S released as a plug is being pulled does not follow a predictable pattern when considering the level that will be reached, the concentration variations during the event, and the time at which the peak concentration will beobserved. Power washing generated lower H_2S concentrations than plug pulling. However, as the task to be performed generally takes time, the 15 min time-weighed average of 15 ppm (STEL) can be- reached after the task started and can be exceeded for a long period of time, which for some of the monitored events was more than 30 min. Finally, monitoring at the storage facilities showed that the risks of exposure to excessive H_2S concentrations during the agitation and emptying of outside, manure storagefacilities were very limited. Results from this study suggest that pig production buildings involving short-term storage of liquid manure may present H_2S exposure risks that have been underestimated until now. All workers should be provided with an H_2S monitor and safety equipment to ensure that workers are protected when the H_2S concentration rises. As well, engineering controls have to be developed to prevent H_2S formation in the manure or H_2S emission into the worker/pig space.