Appendix C 413
Indoor Pollutant
Generation Rate
Indoor Conc - Outdoor Conc + ——————————— Eq. 1
Ventilation Rate + Air
Cleaning Rate + Rate of
Other Removal Processes
4.5.1 Pollutant Sources
The indoor pollutant generation rate is a function of the type and
quantity of indoor pollutant sources. For pollutants that have primar-
ily indoor sources, excluding human bioeffluents, the indoor pollutant
source strength tends to vary over a wider range than the other param-
eters that affect indoor pollutant concentrations. The indoor pollutant
generation rate is often considered to be most important determinant
of the indoor pollutant concentration. Eliminating or minimizing the
emissions of pollutants from indoor sources is a highly effective and
energy efficient means of reducing indoor pollutant concentrations.
4.5.2 Ventilation
In addition to minimizing the emissions of pollutants from indoor
sources, to maintain acceptable IEQ, ventilation with outside air must
be provided at an adequate rate. The ventilation rate, i.e., the rate of
outside air supply, is usually normalized by the floor area (LÆ–1sÆm^2 ),
number of occupants (LÆ–1s per person), or indoor air volume (h–1 or
air changes per hour). The outside air supplied to a building must be
distributed properly to the various rooms to maintain acceptable IEQ
throughout the building. The required rate of outside air supply often
changes with time because of changes in occupancy and indoor pollut-
ant emission rates.
Often, local exhaust ventilation is used in rooms with high pollut-
ant or odor sources. Exhaust ventilation is more efficient in controlling
indoor pollutant concentrations than general ventilation of the entire
space (general ventilation is often called dilution ventilation). Exhaust
ventilation is a means of controlling pressure differentials, as described
below.
4.5.3 Pressure Control
HVAC systems are often used in commercial buildings to maintain
pressure differences between indoors and outdoors or between different