ASHRAE Journal - December 2011 - 124

IAQ APPLICATIONS
The potential role of HVAC systems in controlling exposure to SVOCs. The contamination of indoor environments has been recognized as a signiﬁcant uptake pathway for SVOCs.2 Ventilation is used to remove pollutants and improve indoor air quality, and the effect of ventilation has been studied extensively for VOCs. However, no experimental data in the literature support ventilation strategies to control indoor contamination by SVOCs. The previous analysis under two different air change rates indicates that adjusting the ventilation rate may reduce total indoor airborne SVOCs levels effectively, reducing human exposures. Our recent computational fluid dynamics simulation 11 showed that not only ventilation rate, but also ventilation mode (and thus room air distribution) could also play an important role in controlling the occupants’ exposure to indoor SVOCs. Although the gas-phase concentration of SVOCs in indoor air is normally lower than the concentration of VOCs, a relatively small change in the gas-phase concentration, such as 0.1 ppb, is sufficient for meaningful vapor transport of SVOCs and its consequent partitioning between the gas phase and surfaces of airborne particles and human skin, and has significant influences on indoor SVOC exposures.12 Therefore, the ventilation system can play important roles in controlling the occupants’ exposure to SVOCs. Furthermore, because SVOCs are expected to sorb on particles and dust, particle ﬁltration in an HVAC system may be used to mitigate indoor SVOC exposures in combination with ventilation. With the increase of particles collected on a ﬁlter, SVOCs accumulate on the ﬁlter as well. As long as there is equilibrium between the adsorbed SVOC species and those in the ventilation airstream, no adverse effects are discernible. However, equilibrium can be perturbed by changes in climatic conditions, e.g., temperature and relative humidity. If the equilibrium is perturbed in a fashion that redistributes SVOCs from the ﬁlter into the airstream (e.g., an increase in temperature), the resulting release of SVOCs from a ‘‘loaded’’ ﬁlter may take place. Further investigation is needed to examine the degree to which this could happen, and how to prevent it from occurring. The occurrence of SVOCs in indoor environments is emerging as an important research topic, but SVOCs have not been studied as widely as other classes of indoor pollutants, due in part to the analytical challenges in measuring SVOCs.1 Theoretically, HVAC systems can play an important role in controlling the occupants’ exposure to SVOCs. Research is needed to evaluate how HVAC

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ASHRAE Journal - December 2011

Table of Contents for the Digital Edition of ASHRAE Journal - December 2011
