Real-time indoor sensing of volatile organic compounds during building disinfection events via photoionization detection and proton transfer reaction mass spectrometry

Photoionization detectors (PIDs) are low-cost sensors that are widely used for real-time volatile organic compound (VOC) monitoring in buildings. Performance assessment of PIDs is often based on reference VOC measurements derived from offline, time-integrated sample analysis. Such assessment techniques lack valuable realtime information that is needed to evaluate how PIDs track transient VOC emission events. The objective of this study is to evaluate the real-time performance of a PID in sensing indoor VOC mixtures during building disinfection events through co-location measurements with a state-of-the-art proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). Field measurements were conducted in a tiny house laboratory using an isobutylene-calibrated PID and a PTR-TOF-MS during the use of spray-based disinfectants. The PID and PTR-TOFMS measurements demonstrated that chemical disinfectants are a major source of VOCs in buildings, with the latter revealing the presence of a large diversity of VOCs. In general, the PID was successful in identifying VOC emission events during the application of the disinfectants. Thus, PIDs may be suitable for integration with building automation systems for ventilation control. The PID response was much less than the PTR-TOF-MS response, suggesting that the PID is not efficiently detecting many components of the emitted VOC mixtures. The PID performed best for alcohol-based disinfectants, moderately well for lactic acid- and botanical-based disinfectants, and poorly for disinfectants featuring peracetic and acetic acid. Detailed correlation analysis between the PID and PTR-TOF-MS responses provides a basis for improving the reliability of PIDs in estimating VOC concentrations through application of product-specific correction factors.