Concentration measurement requirements include real-time capability, adequate precision and accuracy, and the availability of suitable calibration standards. Not all of the air emissions of concern from AFOs can be measured by techniques that currently meet these requirements; for example, methods for measuring PM suffer from lack of good calibration standards.

Although measurements of air emission rates have been reported for numerous substances and from a variety of source types (point, line, and area), there are relatively few reports of emission measurements from operations within AFOs, for a variety of reasons. The paucity of emission measurements from AFOs is likely due at least in part to a lack of resources available for this research area. The availability of concentration measurement methods is a prerequisite for emission rate determination. Many of the emission rate methods used for other sources could be adapted to determine emission rates of substances from AFOs. Given the variability of AFOs in such matters as configurations, animal populations, climate, and management practices, the variability of emission rates is expected to be great temporally, spatially, and from one AFO to another.