The need to quantify air emissions from animal feeding operations (AFOs) with relative ease and reasonable certainty continues to rise. Exploration of practical means to reduce air emissions also calls for less sophisticated but reasonably dependable methods to quantify the treatment effect. Although mobile air emissions monitoring units (MAEMUs) capable of precise and real-time emission measurement is the norm for continuous, intensive monitoring of emissions from mechanically ventilated animal facilities, their relative immobility and high cost are limiting the widespread use. Several other methods, such as gas-washing, micro-meteorological, wind tunnel, flux chamber, and mass-balance methods, have been employed to accommodate different measurement needs. Flux chambers have the advantages of being portable, small size, low cost, and less labor requirement. The objectives of this study were: (1) to develop a portable emission flux chamber system (EFC) for in-situ measurement of ammonia (NH3) and carbon dioxide (CO2) emissions from manure; (2) to assess gaseous (NH3 and CO2) emissions of high-rise layer houses with the EFC vs. MAEMU; and (3) to evaluate the adequacy of using the EFC to determine the effects of dietary regimens on ammonia emissions from the layer manure. The preliminary data showed that NH3 emission from the manure surface measured with the EFC was 8% to 16% that of the whole barn measured with the MAEMU, while CO2 emission from the manure surface was 1% to 4% of the barn emission. The preliminary results obtained with EFC concerning the dietary efficacy of ammonia emission reduction were mixed as compared to those obtained with the MAEMU. More evaluation is continuing.