Six case studies are presented for reducing ammonia levels in pig housing of various designs and construction. The pig building’s minimum ventilation rate should maintain a 50-70% relative humidity range unless the NH3 level exceeds the recommended short term exposure limit for workers of 27 mg/m 3. Three main methods are used to reduce NH3 levels: dilution of the gas in the environment by using higher ventilation rates; extracting the NH3 before it reaches the pigs’ level; eliminating the cause of NH3 production such as sealing off a manure storage, or flushing or draining manure out before the start of decomposition.