Ammonia (NH 3 ) emissions at animal-production facilities have significant health and environmental impacts. In addition, recent EPA rulings restricting NH 3 emissions are affecting the profitability and growth of the livestock industry. The accurate measuring of NH 3 emissions is important to avoid unnecessary requirements being placed on livestock producers. Determining NH 3 emissions is expensive and challenging using the current approach of engineering measurement of NH 3 concentrations and air exchange rates. This paper presents a modified N-balance method, which, although it does not distinguish for losses of N as N 2 , NH 3 or NO x 's, it does determine accurately the upper limit on NH 3 -N emissions for both forced and naturally ventilated livestock facilities. The method is based on nitrogen and ash contents and ratio of the inputs (feed, bedding, water, and animals) and outputs (products and waste) of the animal-production systems and does not require measuring total masses of manure from the system. Generalised equations for all classes of livestock operations are presented. This N-balance method was simple, low cost and accurate in predicting the upper limits on NH 3 emissions in the air, leaving a 1.6-million-caged-layer poultry facility with two types of manure management: belt/composting and deep pit. Results from the study showed belt/composting had less than half the total emissions of conventional deep-pit caged-layer systems.