Siloxanes Are the Most Abundant Volatile Organic Compound Emitted from Engineering Students in a Classroom

Direct human emissions are known to contribute volatile organic compounds (VOCs) to indoor air via various mechanisms. However, few measurements that determine the emissions of a full suite of occupant-associated VOCs are available. We measured occupant-related VOC emissions from engineering students in a classroom using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). The dominant compound emitted was a cyclic volatile methylsiloxane (cVMS), decamethylcydopentasiloxane (D5), which is a major inactive ingredient in some personal care products such as antiperspirants. D5 was found to contribute similar to 30% of the total indoor VOC mass concentration as measured by the PTR-TOF-MS. Octamethylcyclotetrasiloxane (D4) and dodecamethylcyclohexasiloxane (D6) were detected at abundances that were 1-2 orders of magnitude lower. The per-person emission rate of these three cVMS declined monotonically from morning into the afternoon, consistent with expectations for emissions from daily morning application of personal care products.