Large Emissions of Low-Volatility Siloxanes during Residential Oven Use

Abstract

Cooking is a source of airborne particles indoors and outdoors. A field study at a residential test house (HOMEChem) included two Thanksgiving-style cooking experiments involving prolonged use of an oven with light use history. Large enhancements of airborne low-volatility siloxanes were observed by three in-situ particle-phase instruments: a high-resolution aerosol mass spectrometer (HR-AMS), semivolatile thermal desorption aerosol gas chromatograph (SV-TAG), and extractive electrospray ionization mass spectrometer (EESI-MS). The combination of these instruments permits quantitatively analyzing time-dependent processes and fates over a wide volatility range with high chemical specificity. Cumulatively, 17 mg and 8.5 mg of bulk siloxane material was emitted indoors and observed in airborne particles during the first and second Thanksgiving experiments, respectively; a peak 5-minute average siloxane concentration of 58 µg/m 3 was measured. Cyclic siloxanes D10-D18 were quantified, and D17 and D16 were the most abundant. We infer that heating of silicone materials inside the oven caused volatilization of cyclic siloxanes and cooler temperatures away from the oven resulted in condensation. Low-volatility siloxanes comprised a surprisingly high fraction of the total emitted submicron particle mass: 18% and 9% during the first and second Thanksgiving experiments, respectively. We estimate ~75% of the low-volatility siloxane mass was ventilated outdoors.

Temperature and indoor environments

“…One well‐known example is the odor generated when turning on a heater for the first time after a long period of time. Heating of deposited materials generates aerosols and increases air concentrations of SVOCs as has been observed for heated surfaces and during cooking 249,250,253,254,256–258 . Cold heat exchanger surfaces, covered in condensed water, are responsible for the removal of polar gases observed during AC operation in several studies 259,260 …”

“…Pans and utensils will tend to remain closer to cooking temperatures of ~300°C or lower under normal use. [248][249][250][251][252][253][254] An important aspect of elevated temperatures in the indoor environment resulting from bas burners, candles, etc., is the thermal formation of NO and NO 2 from atmospheric nitrogen and oxygen. 255 Climate control of air in buildings requires energy transfer to, or from, air to heat and cool to the desired temperature.…”

“…Heating of deposited materials generates aerosols and increases air concentrations of SVOCs as has been observed for heated surfaces and during cooking. 249,250,253,254,[256][257][258] Cold heat exchanger surfaces, covered in condensed water, are responsible for the removal of polar gases observed during AC operation in several studies. 259,260 The elapsed time that air spends at temperatures other than the occupied space is usually relatively short.…”

“…Natural gas flame temperatures approach 2000°C, heating nearby stovetop surfaces. Pans and utensils will tend to remain closer to cooking temperatures of ~300°C or lower under normal use 248–254 . An important aspect of elevated temperatures in the indoor environment resulting from bas burners, candles, etc., is the thermal formation of NO and NO 2 from atmospheric nitrogen and oxygen 255 …”

Human Activities Shape the Indoor Volatile Chemistry

“…Although compounds such as organosilicones in GC-MS are typically associated with undesirable background (septa, column bleeds, etc. ), the HOMEChem campaign revealed the door seal in ovens as a potential source of cyclic organosilicones (46) (47).…”