Whole-House Emission Rates and Loss Coefficients of Formaldehyde and Other Volatile Organic Compounds as a Function of the Air Change Rate

Abstract

Whole-house emission rates and indoor loss coefficients of formaldehyde and other volatile organic compounds (VOCs) were determined from continuous measurements inside a net-zero energy home at two different air change rates (ACHs). By turning the mechanical ventilation on and off, it was demonstrated that formaldehyde concentrations reach a steady state much more quickly than other VOCs, consistent with a significant indoor loss rate attributed to surface uptake. The first order loss coefficient for formaldehyde was 0.47 ± 0.06 h–1 at 0.08 h–1 ACH and 0.88 ± 0.22 h–1 at 0.62 h–1 ACH. Loss rates for other VOCs measured were not discernible, with the exception of hexanoic acid. A factor of 5.5 increase in the ACH increased the whole-house emission rates of VOCs but by varying degrees (factors of 1.1 to 3.8), with formaldehyde displaying no significant change. The formaldehyde area-specific emission rate (86 ± 8 μg m–2 h–1) was insensitive to changes in the ACH because its large indoor loss rate muted the impact of ventilation on indoor air concentrations. These results demonstrate that formaldehyde loss rates must be taken into account to correctly estimate whole-house emission rates and that ventilation will not be as effective at reducing indoor formaldehyde concentrations as it is for other VOCs.

Volatile organic compound emissions during HOMEChem

“…Because of analytical constraints in sampling and in typical chromatographic methods, most published full‐scale residential studies have low time resolution (1–24 h or longer) and include a limited set of target compounds (<100). Recent advances in chemical ionization mass spectrometry allow for highly time resolved and chemically speciated measurements of hundreds of indoor VOCs 1,15–20 . Huangfu et al used the high time resolution of proton transfer reaction mass spectrometry (PTR‐MS) to infer a temperature and air‐change rate (ACR) dependence of VOC mixing ratios in multiple unoccupied homes 19 .…”

“…Recent advances in chemical ionization mass spectrometry allow for highly time resolved and chemically speciated measurements of hundreds of indoor VOCs. 1,[15][16][17][18][19][20] Huangfu et al used the high time resolution of proton transfer reaction mass spectrometry (PTR-MS) to infer a temperature and air-change rate (ACR) dependence of VOC mixing ratios in multiple unoccupied homes. 19 Liu et al determined building-associated VOC emissions in an occupied home by numerically filtering data for compounds that have steady rates of emission, rather than the episodic emission characteristic of occupancy and activities.…”

A Time-Varying Model for Predicting Formaldehyde Emission Rates in Homes

“…Increasing ventilation rate would increase the concentration gradient between material air surface layer and the room air, leading to an increment of whole house formaldehyde emission rate, as suggested by previous studies [ 17 , 22 , 23 , 24 , 25 , 26 ]. Specifically, ventilation has been shown to increase formaldehyde emissions, while still providing a net-reduction in indoor concentrations.…”

Residential air‐change rates: A critical review

“…Ideas about the nature of these relationships have been explored, mainly in theoretical studies 130,137,138 . Empirical evidence about actual behavior in occupied residences under real‐life conditions is scant 133,139 …”

“…130,137,138 Empirical evidence about actual behavior in occupied residences under real-life conditions is scant. 133,139 Important challenges remain to better understand residential air-change rates. One important detail is to differentiate between the variation in air-change rates across the building stock versus variation in air-change rates over time in any individual house.…”