Design and validation of a mobile air filter testing laboratory for animal agricultural applications

Abstract

The US swine industry is shifting towards filtered fresh-air ventilation systems that use pleated filters to improve breeding herd health and reduce airborne disease outbreak frequency. Loaded filters reduce airflow causing a poor environment and elevated energy use. Typical axial fans cannot efficiently maintain the rated differential pressure (DP; 100 Pa) for pleated filters; hence, a lower design filter DP (37 Pa) is used and consequently, more filters are required to achieve design maximum ventilation. Large, common filter banks for multiple staged fans presents significant challenges in using continuous DP measurement to assess filter life, making it impossible to separate filter loading DP from overall airflow DP. A mobile air filter testing (MAFT) laboratory is needed to provide timely farm-to-farm testing of on-site filters by accurately measuring airflow at given DPs to identify filter end-of-life and enable research on spatiotemporal filter loading characteristics. The MAFT laboratory consisted of a 4.6 m long acrylic test duct mounted in an enclosed trailer capable of operating at 37 Pa DP across primary and secondary filter combinations for 2,820 to 28,200 L min^-1 airflows. Test duct calibration (R²>0.99; RMSE=1.40×10² L min^-1) at BESS Labs and validation against a third-party laboratory (34 loaded filters from commercial swine facilities) showed good agreement (p<0.0001). Relative expanded uncertainty was calculated to range from 1.5% to 5% (23,619 to 5,721 L min^-1). The MAFT laboratory provides a unique approach for testing agricultural filter performance directly on-farm to eliminate the time and cost to test filters at third-party laboratories