It is assumed that as pig mass per unit area increases, the
odor emission rate also increases. This assumption was used
by most setback distance guidelines developed by researchers
and governments (Guo et al., 2004). As stated previously,
the effect of animal units on odor concentration and
emissions was not conclusive for the four types of swine
rooms. In the nursery rooms, average pig density varied from
16 to 91 kg/m2, while in the finishing rooms it ranged
between 6 and 138 kg/m2 over the year. No correlation was
found between odor concentration or odor emission rate and
pig density for both types of rooms (P > 0.05). Low odor
concentration and emissions sometimes occurred when pig
densities were high, and sometimes high odor emissions were
found when pig densities were low. Therefore, animal units
or animal density of nursery and finishing barns may not
represent the odor concentrations and emissions.