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Ventilation rate (VR) is one of the two key elements for quantifying aerial emissions from animal production facilities. Direct, continuous measurement of building VR can be challenging and impractical under certain circumstances, e.g., naturally ventilated animal housing or a large number of ventilation fans in the building. This study examined the suitability of estimating VR of broiler houses with built-up litter (mixture of manure and bedding), when supplemental heating was not in use, through either carbon dioxide (CO2) balance or the relationship of VR to CO2 concentration difference between exhaust and inlet air. The reference VR was based on direct measurement by continuously monitoring operation of the in-situ calibrated exhaust fans. The comparative analysis of the direct method vs. each indirect method was conducted for a measurement integration time (MIT) of 10, 30, 60, or 120 min. The analyses revealed that MIT of 30 min or greater resulted in non-significant differences in VR between the indirect and direct methods. The broiler building VR (m3 s-1) may be related to the exhaust-inlet CO2 concentration difference (ΔCO2, ppm) as VR (±3.0) = 4456 (±41) ΔCO2-0.786(±0.019) at 30 min MIT. The VR may also be determined by the CO2 balance method (including litter CO2 generation) with a correction factor of 0.97 at MIT of 30 to 120 min. If litter CO2 generation is omitted from the total building CO2 production, the actual VR may be estimated by applying a correction factor of 1.077 to the bird respiration CO2 balance VR. Hence, the CO2 balance or concentration difference method offers a viable alternative or supplemental check for quantifying building VR under certain conditions where direct, continuous VR measurement is not feasible. [ABSTRACT FROM AUTHOR]

Accurate ventilation rate (VR) data are essential to maximizing the quality of aerial emission measurements. The Fan Assessment Numeration System (FANS) has been widely used by U.S. researchers in measuring aerial emissions from mechanically ventilated livestock and poultry facilities. The FANS device is used to measure airflow rates of ventilation fans in situ, thereby developing fan performance curves under field conditions. The FANS device was originally intended to be placed upstream of the fan to be calibrated. However, certain field situations make it impractical to apply the FANS device as such. This study was conducted to assess use of the FANS device downstream of a ventilation fan, with the gaps between the FANS device and the discharge cone of the exhaust fan sealed using a non-permeable fabric. Nine exhaust fans (1.22 or 1.32 m diameter) in laying hen and turkey houses were tested with the FANS device placed upstream and downstream for a building static pressure range of 10 to 40 Pa. The results revealed that downstream placement of the FANS device yielded 0.6% ± 0.4% to 4.0% ± 0.9 % (mean ± SE) higher but not significantly different (P > 0.28) VR values as compared to upstream placement for the exhaust fans tested. This magnitude of discrepancy is considered acceptable for in situ measurement of fan performance. [ABSTRACT FROM AUTHOR]

Analysis of the propagation of measurement error into a computed quantity such as building aerial emissions provides insight into which measurements are most critical and which would have the most impact on the computed quantity if improved. An analysis of different instrument measurements, sampling periods, and sites together comprise an objective means of determining optimal sampling strategies for measurements used to compute aerial emissions from livestock facilities. This article describes the uncertainty analysis for a measurement system used in emissions research, and how it can lead to improvements in measurement system design and implementation to obtain estimates of uncertainty in emissions. The system analyzed was used in a broiler house emission monitoring project that was part of the U.S. EPA Air Consent Agreement. The project required U.S. EPA category I Quality Assurance Project Plan (QAPP) Data Quality Objectives (DQO), which were developed from this uncertainty analysis. Results of the uncertainty analysis suggest that the combined standard uncertainty in ammonia emission from broiler houses in the study was typically less than 6%; it increased with uncertainty in ventilation rate, but decreased as ventilation rate and number of fans running increased. The combined standard uncertainty was quantified for normal measurement conditions (Case 1) and for conditions in which the instrumentation was at the calibration threshold (Case 2). A key conclusion was that, for the measurement system employed in this project, uncertainty in the measurements associated with ventilation rate are the major contributors to emissions rate uncertainty (ranging from 78% to 98.9% of combined standard emission uncertainty). [ABSTRACT FROM AUTHOR]