Air Quality and Emission Measurement Methodology

Reliable measurements of air quality and emissions at large livestock buildings with inherently large spatial and temporal variations of pollutant concentrations are relatively difficult and expensive. Appropriate methodologies for such measurements are not readily apparent and techniques and strategies vary widely. Several important technical issues need to be addressed by an air pollutant emission measurement plan. This article describes comprehensive field measurements of indoor air quality and air pollutant emissions at eight commercial swine finishing buildings. The objective of the field test was to evaluate the effect of a manure additive on concentration and emission of ammonia, hydrogen sulfide, and odor. Continuous measurements of gases, ventilation rate, building static pressure, inside and outside temperature and humidity, and wind speed and direction were conducted at four naturally–ventilated buildings and four mechanically–ventilated buildings. Air was pumped continuously from inside each building into air–sampling manifolds. One air stream was drawn from beneath the floor to assess pit headspace air concentrations. Another air stream was drawn from ventilation exhaust points to assess inside gas concentrations and building emission rates. Gas analyzers were switched between sampling manifolds on 10– to 15–min sampling intervals. Ammonia was measured with chemiluminescence NOx analyzers after conversion to nitric oxide. Hydrogen sulfide was converted to sulfur dioxide and measured with pulsed–fluorescence, sulfur dioxide analyzers. Odor samples were collected in bags and evaluated using olfactometry. Gas and odor emission rates were determined by multiplying mean gas concentrations in the exhaust air by ventilation airflow rates. Ventilation rates of naturally–ventilated buildings were estimated using sensible heat and carbon dioxide balances. Ventilation rates of mechanically–ventilated buildings were determined by monitoring wall fan operation and directly measuring airflow of some variable–speed pit fans with full–size impeller anemometers. Labor and equipment requirements, pitfalls, problems, and solutions to problems of field studies are discussed. Several recommendations for future studies of this type were developed based on experience gained during this measurement campaign.