a hog-growing facility. Can. J. Anim. Sci. 7I: 2'71-2'77.In order to assess the effects of ventilation rate, temperature, relative humidity and source of air on bioaerosol levels and dust with particle size < l0 pm, a total of 120 pigs housed in 12 pens in two separate rooms were used. Pigs averaged 30 kg initially and the trials were discontinued when2O% of the pigs were marketed. A six-stage Andersen sampler and a light scattering particle counter were used to determine bioaerosols and respirable dust (0.1-10 pm), respectively. Total bioaerosols were assessed using Trypticase Soy Agar. Potato Dex-