Kinetic Analysis of Competition between Aerosol Particle Removal and Generation by Ionization Air Purifiers

Abstract

Ionization air purifiers are increasingly used to remove aerosol particles from indoor air. However, certain ionization air purifiers also emit ozone. Reactions between the emitted ozone and unsaturated volatile organic compounds (VOC) commonly found in indoor air produce additional respirable aerosol particles in the ultrafine (<0.1 microm) and fine (<2.5 microm) size domains. A simple kinetic model is used to analyze the competition between the removal and generation of particulate matter by ionization air purifiers under conditions of a typical residential building. This model predicts that certain widely used ionization air purifiers may actually increase the mass concentration of fine and ultrafine particulates in the presence of common unsaturated VOC, such as limonene contained in many household cleaning products. This prediction is supported by an explicit observation of ultrafine particle nucleation events caused by the addition of D-limonene to a ventilated office room equipped with a common ionization air purifier.

Secondary organic aerosol from ozone-initiated reactions with terpene-rich household products

“…was reported for limonene injected into an office in which an air-cleaning device that produces ozone as a byproduct was operated (Alshawa et al, 2007).…”

“…Optical particle counters (OPC) typically measure only particles that are 100 nm or larger and thus cannot characterize the ultrafine particles that are an essential component of particle nucleation and growth. A few studies have characterized ultrafine particles using a scanning mobility particle sizer (SMPS) to investigate nucleation and growth in these cases: (a) use of a pine-oil based cleaner in the presence of ozone (Long et al, 2000); (b) peeling of oranges in the presence of ozone (Vartainen et al, 2006); and (c) adding limonene to an office environment in which an ionizing air purifier was used (Alshawa et al, 2007).…”

Enhancement of the deposition of ultrafine secondary organic aerosols by the negative air ion and the effect of relative humidity

“…The three researches above were conducted with NaCl particles. However, the result of Alshawa et al (2007) indicates that the ion generator acts as an air contaminator instead of an air cleaner. Thus, the air ion generators perform better on the removal of NaCl particles than the removal of SOA particles.…”

“…However, most NAI generators on the market may emit ozone and then result in the increase of the mass concentration of ultrafine (nano-scale) and fine particles in the presence of biogenic volatile organic compounds (BVOCs), such as terpenoids, limonene, a-pinene, and b-pinene, etc. (Alshawa et al, 2007;Waring et al, 2008). BVOCs will react with ozone and then generate secondary organic aerosols (SOAs) (Claeys, 2004;Chen and Griffin, 2005;Alshawa et al, 2007;Lee and Hsu, 2007;Sarwar and Corsi, 2007;Waring et al, 2008;Huang et al, 2011;Yu et al, 2011b;Bernard et al, 2012;Jonsson et al, 2006).…”

“…(Alshawa et al, 2007;Waring et al, 2008). BVOCs will react with ozone and then generate secondary organic aerosols (SOAs) (Claeys, 2004;Chen and Griffin, 2005;Alshawa et al, 2007;Lee and Hsu, 2007;Sarwar and Corsi, 2007;Waring et al, 2008;Huang et al, 2011;Yu et al, 2011b;Bernard et al, 2012;Jonsson et al, 2006). Ultrafine particles may cause harmful health effects to human beings because they can penetrate deeply into the alveoli of lung or brain via neuronal translocation through olfactory nerves (Vallyathan and Gwinn, 2006).…”