Estimating the effects of external pollution on indoor air quality.

The effect of external pollution levels on indoor air quality is a subject of growing interest, especially with the increasing application of natural ventilation in urban areas. The analysis described in this paper allows the effects of varying external pollution levels to be estimated for any configuration of ventilation system, natural or mechanical. The analysis takes into account filter efficiency and position, internal pollutant sources, degree of re-circulation and varying fresh air rates. By developing simplified dynamic equations rather than steady state formulations, the effects of varying "fresh" air rates based on the external pollution level can also be examined.