Wintertime factors affecting contaminant distribution in a swine farrowing room

Abstract

An estimated 200,000 to 500,000 U.S. workers in concentrated animal feeding operations (CAFOs) are at risk of adverse respiratory outcomes from exposures to indoor contaminants. In the wintertime, general ventilation is minimized in the Midwest due to high heating costs required to maintain indoor temperatures optimal for animal production. Pit fans typically operate to exhaust under-floor manure pits, but little other fresh air intake exists. Many operators believe that these systems are sufficient to reduce contaminant concentrations within the building during winter. Investigating whether these pit fans provide sufficient protection against classic CAFO contaminants during minimal wintertime ventilation was warranted. Direct-reading instruments were used to measure and record concentrations of multiple contaminants using both fixed-area and mobile contaminant mapping in a farrowing room during a Midwest winter. With the exception of CO, concentrations were significantly (p<0.001) higher with the pit fan off compared with those with the pit fan on. Additional analyses identified that significant changes (p<0.001) in mean room concentrations of respirable dust (decreased, 77% with pit fan off and 87% with pit fan on) and CO2 (increased, 24%) over the 5-hr study periods and that multiple fixed-area monitors rather than the much-used, single center-of-room monitor provided a more conservative (e.g., protective) assessment of room concentrations. While concentrations did not exceed occupational exposure limits from OSHA or ACGIH for individual contaminants, recommended agricultural health limits from exposure-response studies suggested in the literature were exceeded for respirable dust, CO2, and NH3, indicating a need to consider personal exposures and control options to reduce contaminant concentrations in farrowing rooms. Pit fans reduced NH3 and H2S concentrations, but these fans may not be sufficient to control dust and eliminate the need for secondary exposure prevention methods.

Figure 1

Schematic diagram of the swine farrowing room and attached hallway. Boxed letters A–G indicate fixed sampling positions. Letters by the sampling positions indicate the equipment deployed at that position: P = photometer (respirable dust); V = VelociCalc (CO₂), M = multi-gas (CO, H₂S, NH₃). All three devices were used at the 43 mobile monitoring positions, indicated by the dots in the aisles.

Figure 2

Respirable dust concentration contour for (a) Day 1 with pit fan on, and (b) Day 2 with pit fan off

Figure 3

Carbon dioxide concentration contour for (a) Day 1 with pit fan on, and (b) Day 2 with pit fan off