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Hydrogen sulfide assessment in shallow pits swine housing and outside manure storage facilities

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  024084,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.9537) @2002
Authors:   L. Chénard, S.P. Lemay, C. Laguë
Keywords:   gas monitoring, manure management, plug pulling, occupational health, hydrogen sulphide, hydrogen sulfide, H2S, worker exposure, liquid manure, gases, manure storage, powerwashing

Hydrogen sulfide (H2S) is produced by anaerobic bacterial decomposition of liquid manure. High H2S concentrations have been measured when manure is being agitated, particularly in deep pit swine buildings and in confined spaces such as transfer pits and manure tanks. However continuous monitoring in shallow pit buildings showed that background concentrations of H2S remain very low. In Saskatchewan, some recent incidents have lead us to believe that certain manure management activities can potentially release high concentrations of H2S in the shallow pit barns atmosphere. The objectives of the monitoring project reported herein were to evaluate worker exposure to H2S during the completion of the following tasks: 1. emptying of in-barn shallow manure pits; 2. power washing of barn rooms and, 3. 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 H2S. The maximum values recorded during some of the monitored events reached 1,000 ppm. The H2S 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 be observed. Power washing generated lower H2S 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 a while after the task started (close or more than an hour after the start) and be exceeded for a long period of time, which for some of the monitored events, was more than 30 min. Finally, the monitoring at the storage facilities showed that the risks of exposure to excessive H2S concentrations during the agitation and emptying of outside manure storage facilities were very limited. Results from this study suggest that pig production buildings involving short term storage of liquid manure may present H2S exposure risks that have been underestimated until now. All workers should be provided with a H2S monitor and safety equipment to insure that danger is known when the H2S concentration arises and that workers are protected. As well, engineering controls have to be developed to prevent H2S formation in the manure or H2S emission into the worker/pig space.

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