Dust concentrations in animal buildings can be reduced by sprinkling a small quantity of canola (rapeseed) oil on the floor. The efficiency of dust reduction was expected to be dependent on the frequency and quantity of oil application. Canola oil was sprinkled at 6 application rates (QF1 to QF6) in 3 identical pig growing/finishing rooms to examine the effect of oil application frequency and quantity on dust concentration in the room air. For the 6 oil application rates, dust concentration was reduced by 37-89% with an overall mean reduction of 71% for modified respirable dust (0.5-5 micro m) and 76% for inhalable dust (>0.5 micro m). At the same total volume of oil sprinkled, a higher oil application frequency was more effective than a lower application frequency in terms of dust reduction. However, sprinkling more often than once a day is difficult when the oil application is less than 10 ml/m2 per day. The more oil sprinkled, the more dust could be reduced. Variable daily dosages (from 30 to 10 ml/m2) for oil sprinkling had a higher efficiency of dust reduction than a constant daily dosage (20 ml/m2).