Effect of Ventilation Systems and Air Filters on Decay Rates of Particles by Indoor Sources in an Occupied Townhouse.
Effect of Ventilation Systems and Air Filters on Decay
Rates of Particles by Indoor Sources in an Occupied
Howard-Reed, C.; Wallace, L. A.; Emmerich, S. J.
Atmospheric Environment, Vol. 37, No. 38, 5295-5306,
fine particles; coarse particles; deposition;
filtration; residential indoor air quality; equations
Several studies have shown the importance of particle
losses in real homes due to deposition and filtration;
however, none have quantitatively shown the impact of
using a central forced air fan and in-duct filter on
particle loss rates. In an attempt to provide such data,
we measured the deposition of particles ranging from 0.3
to 10 m in an occupied townhouse and also in an
unoccupied test house. Experiments were run with three
different sources (cooking with a gas stove, citronella
candle, pouring kitty litter), with the central heating
and air conditioning (HAC) fan on or off, and with two
different types of in-duct filters (electrostatic
precipitator and ordinary furnace filter). Particle
size, HAC fan operation, and the electrostatic
precipitator had significant effects on particle loss
rates. The standard furnace filter had no effect.
Surprisingly, the type of source (combustion vs.
mechanical generation) and the type of furnishings
(fully furnished including carpet vs. largely
unfurnished including mostly bare floor) also had no
measurable effect on the deposition rates of particles
of comparable size. With the HAC fan off, average
deposition rates varied from 0.3 h-1 for the smallest
particle range (0.30.5 m) to 5.2 h-1 for particles
greater than 10 m. Operation of the central HAC fan
approximately doubled these rates for particles <5 m,
and increased rates by 2 h-1 for the larger particles.
An in-duct electrostatic precipitator increased the loss
rates compared to the fan-off condition by factors of
510 for particles <2.5 m, and by a factor of 3 for
2.55.0 m particles. In practical terms, use of the
central fan alone could reduce indoor particle
concentrations by 2550%, and use of an in-duct ESP could
reduce particle concentrations by 5585% compared to