Update on ammonia generator for maintaining a set indoor gas concentration for poultry health research

Abstract. Ammonia gas (NH₃) generators were operated continuously for six weeks to maintain a concentration of 50.5 parts per million (ppm) of ammonia gas in two controlled environmental chambers to study poultry physiological response to sustained elevated levels of ammonia gas. The controlled environmental chambers had dimensions of 3.7 x 4.3 x 2.4m (12 x 14 x 8 ft) and were equipped with a 1.5 m³/s (3,060 cfm) recirculation system that regulated indoor temperature levels and a 0.06 m³/s (130 cfm) exhaust fan that exchanged indoor air for fresh outdoor air. The ammonia generators released ammonia gas and water vapor using ultrasonic humidifiers filled with commonly available ammonia cleaning liquid with output controlled by a metallic oxide MQ-137 ammonia gas sensor connected to an Arduino-based control system. Relative humidity regulation was not functional in the chambers, which presented challenges for the gas sensors used to control NH₃ concentration, and frequent calibration adjustments of the gas sensors was necessary. Previous results demonstrated two ammonia generators operating together in one chamber filled with 3.8L (1 gallon) each of 2% ammonia cleaning liquid produced 49.45 ± 0.79 ppm of ammonia gas for a duration of 30 hours before running empty. Results from this six-week experiment show that 3.8L (1 gallon) of 10% ammonia cleaning liquid in a single ammonia generator in each chamber could maintain the target gas level of 51.24 ± 1.53 ppm for a duration of 195 hours before refilling was required. The higher strength ammonia solution required fine tuning of the control system to achieve the same accuracy, but it could respond to environmental changes more rapidly and resulted in less run time to maintain the same gas levels.