A current research project based in the UI College of Public Health’s Great Plains Center for Agricultural Health (GPCAH) is investigating methods to improve air quality in swine farrowing buildings(1). The research team developed models to estimate room concentrations of multiple indoor contaminants (ammonia, dust, hydrogen sulfide, carbon monoxide, and carbon dioxide) and conducted field monitoring to evaluate the effectiveness of using ventilation and engineering controls.
In both modeling and field work, the researchers found that CO2 concentrations exceeded recommended workplace limits for swine workers(2) (1540 ppm) over the entire winter season and also exceeded one-half the Occupational Safety and Health Administration permissible exposure limit (PEL=5000 ppm), which is based on exposure to a single contaminant (unlike what exists in swine buildings). Sources of CO2 in livestock production include both animal respiration and combustion products from heaters.
Since controlling animal breathing is infeasible, the team evaluated whether the unvented heaters commonly used throughout the Midwest were a significant contributor to high CO2 levels measured in livestock buildings. In fall 2014, researchers installed new gas-fired heaters, the Effinity93, in a test barn. The team measured concentrations throughout the following winter, comparing them to that of the previous winter with traditional unvented heaters.
To protect the unit from dust, fresh air intake to the combustion device was from outside the farrowing building, and combustion gases were exhausted from the unit to outside the building. The investigators identified that CO2 was reduced by 800 ppm with the new heaters.
Another 200 ppm difference in CO2 between seasons was attributed to colder outdoor temperature and larger in-room animal population in the winter with the older unvented heaters. Other vented gas-fired heaters are available, and the researchers recommend substituting unvented heaters with vented units that have stainless steel internal components, which should improve the lifespan of the heater when used in livestock environments containing ammonia.
This story originally appeared in the September issue of Farm Families Alive & Well.