PMF Analysis of PTR-MS Measurements Provides an Assessment of VOC Sources in an Occupied Student Office

Although indoor volatile organic compounds (VOCs) can cause adverse health effects, the relative importance of different sources in indoor environments and the factors controlling them remain uncertain. In this work we analyzed real-time PTR-MS measurements using positive matrix factorization (PMF) to determine VOC sources in an occupied student office. The PMF analysis was conducted using a subset of VOC data that did not include VOCs largely from personal care products, as they exhibited episodic, unpredictable behavior. The major sources were identified as prompt human emissions, emissions from building materials, outdoor air, and long-lived human oxidation, accounting for 21%, 44%, 9%, and 25% of the total VOCs, respectively. In addition to direct emissions, humans contributed to indoor VOCs through skin oil surface ozonolysis and surface re-emission, resulting in sustained impact hours after occupants had left the office. The PMF analysis demonstrated that the outgassing rate of VOCs from building materials is positively impacted by relative humidity and that most VOCs arise from indoor processes and chemistry, not via introduction of outdoor air. Overall, this work delivers an assessment of indoor VOC sources, advancing our understanding of their relative importance and the key factors governing their contributions within occupied environments.