Indoor air quality (IAQ) is a growing concern for both public
health and occupational health sectors. Health effects due to poor
IAQ can result from a wide variety of pollutants, including airborne
particles, such as combustion products, chemical evaporates, and
microbes or allergens [1,8]. This is a widespread issue that can affect
everyone. Respondents to an EPA sponsored human activity study
reported spending an average of 87% of their time indoors [24]. It
has been shown that air filtration is beneficial for the health of
occupants [14]. Emerging technologies developed to combat these
issues have led to an increasing use of air purifiers within various
indoor environments such as homes and workplace. Among
various air purifiers available today, those using true high efficiency
particulate air (HEPA) filters have been proven to reduce the concentrations
of indoor air particles without producing harmful byproducts
[5,6]. At the same time the highly efficient purifiers are
often noisy.
A major IAQ concern in homes and workplaces located near
highways in urban areas is exposure to traffic related airborne
particles (TRAP), which have been shown to exacerbate the effects
of existing asthma, as well as increase the incidence of asthma and
other respiratory conditions [19]. It has been shown that a decrease
in TRAP by as little as 25% can have a significant impact on asthma
control in adults [13]. HEPA air purifiers can be effective at reducing
the concentration of indoor air particles [11,34]. However, very little
is known about the efficiency of HEPA air purifiers against TRAP. In
trying to reduce indoor concentrations of TRAP, ultrafine
combustion-generated diesel particles (diameter