Complaints and lawsuits by neighbors and urban dwellers have turned attention toward odors and methods of controlling them. Other concerns for air quality concern those who work in the buildings, and the hogs themselves. High levels of noxious gases in confinement buildings have caused persons to experience irritation in breathing. Dead hogs also have been reported when noxious gas levels became critically high. Gases and odors in a confinement facility result from bacterial action on biodegradable parts of swine waste.
Gases produced in greatest volume are methane, carbon dioxide, ammonia and hydrogen sulfide.
A complicated group of volatile organic substances also contribute to the odor complex in swine buildings. This group contains amines, mercaptans, alcohols, carbonyls and sulfides in trace amounts. Methane, the gas produced in greatest volume during the anaerobic stabilization process, results from organic acids being degraded. This gas usually escapes to the atmosphere and is a potential air pollutant. Carbon dioxide, the second most abundant gas in the anaerobic process, is also produced as organic acids are degraded.