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Environmental Sensors The smell of ammonia near intensive farming areas can be very unpleasant. Ammonia concentrations on farms can breach the allowed exposure limit. This results in unhealthy situations for farmers and animals inside the stables, chicken houses, etc. Also, ammonia is considered an important pollutant species due to its role as a precursor in fine particulate matter formation (which causes respiratory problems) and its impact on ecological nitrogen balance. Consequently, the EPA, USDA, and various state agencies have shown strong support to develop and test ammonia monitoring instrumentation. These types of sensors must be able to measure ammonia over a large concentration range, covering sites such as: ►     Poultry houses, where the concentration can be as high as 150 ppm. ►     Dairy wastewater lagoons, where the concentration can be less than 10 ppm. ►     At property fence lines, where regulatory reports mandate maximum ammonia concentrations of 500 ppb. As such, sensors need to have a sensitivity of better than 150 ppb to resolve concentrations at the fence line, yet also require more than three orders of magnitude linearity in order to be deployed within the facilities, all with a measurement time of approximately I mm. Moreover, agricultural sensors must be able to withstand the ambient conditions, which include heavy dust loading, moisture from humidity, condensation and rain and vibrations from instrument use. The proposed sensor can properly address all these challenges. In order to better define the emission rate of ammonia gas being produced by a typical agricultural facility sensors that are inexpensive, reversible, sensitive, and fast are necessary. To address these challenges, the proposed ammonia gas sensor offers the following features:      • small, efficient, and inexpensive      • reversible with fast response time (0.1s)      • less than 1ppm sensitivity      • good selectivity      • wide operating range (from 10 ppb to 1000 ppm)      • infrequent and easy calibration      • unaffected by humidity In order to determine the value of treatment or management techniques for reducing indoor ammonia gas, there is a need to accurately determine the emission rates. The proposed system will utilize several sensors (nodes) to wirelessly monitor the indoor ammonia level, and activate a ventilation system if ammonia levels should breach the low exposure limit level.