For the CO2 mass balance method, the CO2 gain of a room
from the incoming air (345 ppm) and the CO2 produced by
the animals is equal to the CO2 loss through the exhaust air.
The CO2 produced by the manure was considered negligible.
The room CO2 concentration was measured directly from the
air samples immediately after the samples were collected.
CO2 concentrations lower than 3,000 ppm were measured by
a Guardian Plus infrared gas monitor (accuracy: ±2% for 0
to 3,000 ppm, Edinburgh Sensors, Ltd., Hingham, Mass.),
and CO2 concentrations over 3,000 ppm were measured by
gas chromatography in the Soil Science Laboratory, University
of Saskatchewan. Pig number and weight were recorded
for each room. The total CO2 loss from a room was the
difference in the CO2 concentrations of the exhaust and
incoming air multiplied by the ventilation rate. Room and
outdoor temperature and relative humidity were also recorded.