The total value of dairy, livestock, and poultry production in 2002 was $124 billion dollars, more than half of the total value of all US agricultural production.  As the number of farms has been decreasing, production on larger farms has increased, leading to concerns related to the impact of this production on the environment.  Areas of concern have revolved around gaseous emissions (NH₃, CH₄, N₂O and VOCs), particulate matter (PM₁₀ and PM_2.5), and bioaerosols from animal housing and manure management and storage systems.  It is estimated that >70% of total U.S. NH₃ emissions and 3.3% of CO₂e (CH₄ + N₂O) emissions originates from the livestock and poultry sectors. As a response several federal and state air quality regulations have been developed to control emissions from the livestock and poultry sectors.  In addition, there is an increasing focus on improving on farm emissions estimates and developing management strategies to reduce these emissions.  While regulatory actions are likely inevitable, it is imperative that we develop realistic on-farm estimates of emissions and determine how management practices can work to reduce system level emissions for a range of species and climatic conditions.