A portable and relatively low-cost monitoring unit (PMU) for continuous measurement of ammonia and carbon dioxide in CAFO (poultry in particular) applications has been developed and partially compared with an EPA-approved measurement method. The PMU utilizes sampling and purging cycles to overcome the sensor saturation characteristic of electro-chemical NH3 sensors. Preliminary comparative results show that performance of the PMU is quite comparable to the sophisticated, highercost, and less portable mobile lab method. For the range of ammonia level typical of commercial poultry buildings, the PMU is expected to produce emission rate data of reasonable quality when combined with properly measured or determined building ventilation rate.