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It is a common practice in the midwestern United States to raise swine in buildings with under-floor slurry storage systems designed to store manure for up to one year. These so-called "deep-pit" systems are a concentrated source for the emissions of ammonia (NH 3 ), hydrogen sulfide (H 2 S), and odors. As part of a larger six-state research effort (U.S. Department of Agriculture-Initiative for Future Agriculture and Food Systems Project, "Aerial Pollutant Emissions from Confined Animal Buildings"), realtime NH 3 and H 2 S with incremental odor emission data were collected for two annual slurry removal events. For this study, two 1000-head deep-pit swine finishing facilities in central Iowa were monitored with one-year storage of slurry maintained in a 2.4 m-deep concrete pit (or holding tank) below the animal-occupied zone. Results show that the H 2 S emission, measured during four independent slurry removal events over two years, increased by an average of 61.9 times relative to the before-removal H 2 S emission levels. This increase persisted during the agitation process of the slurry that on average occurred over an 8-hr time period. At the conclusion of slurry agitation, the H 2 S emission decreased by an average of 10.4 times the before-removal emission level. NH 3 emission during agitation increased by an average of 4.6 times the before-removal emission level and increased by an average of 1.5 times the before-removal emission level after slurry removal was completed. Odor emission increased by a factor of 3.4 times the before-removal odor emission level and decreased after the slurry-removal event by a factor of 5.6 times the before-removal emission level. The results indicate that maintaining an adequate barn ventilation rate regardless of animal comfort demand is essential to keeping gas levels inside the barn below hazardous levels.

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Ammonia (NH3) emission from a grow‐finish swine (Sus scrofa) building with an underfloor manure storage pit was evaluated during warm weather from 26 June to 25 September. Average daily mean (ADM, covering all measurement days) outdoor temperature was 21.8°C. Ammonia concentrations, ventilation rates, and temperatures were continuously measured or recorded and 88 d of reliable data were obtained. Air samples were taken at wall and pit exhaust fans and in the pit headspace. The NH3 concentrations were monitored on‐site with a chemiluminescence NH3 analyzer. Ventilation rates were calculated based on operation of five wall fans, four pit fans, and the fan static pressure. The NH3 emission rates were calculated by multiplying simultaneously measured NH3 concentrations and ventilation rates of wall and pit exhaust fans. The ADM of building NH3 concentration (mean concentration of all sampling locations) was 3.9 mg m−1. The ADM building NH, emission (sum of the emissions from all ventilation fans) was 11.2 kg d−1, equivalent to 145 g d−1 per AU (animal unit = 500 kg animal weight). The ADM emission per AU was higher than other reported values, probably due to warmer temperatures and higher ventilation rates. The building NH3 concentrations were inversely proportional to the indoor temperatures (r = −0.66) and ventilation rates (r = −0.59) and correlated well to total pig weight (r = 0.49). The building NH3 emission rates were correlated to total pig weights (r = 0.52) and ventilation rates (r = 0.41) and were not well correlated to indoor temperatures (r = 0.12).

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