Thymol-based botanical disinfectants have emerged as natural alternatives to traditional chemical disinfectants given their effectiveness as antimicrobial pesticides and ability to inactivate SARS-CoV-2. This study investigates the impact of botanical disinfectants on indoor air chemistry and human exposure. Controlled surface disinfection experiments were conducted in a mechanically ventilated zero-energy tiny house laboratory. Volatile organic compounds (VOCs) and aerosol size distributions were measured in real-time (1 Hz) with a proton transfer reaction time-of-flight mass spectrometer and a highresolution electrical low-pressure impactor, respectively. Botanical disinfectant spray and wipe products drove sudden changes in the chemical composition of indoor air. Mixing ratios of monoterpenes (C 10 H 16 ) and monoterpenoids (C 10 H 14 O, C 10 H 16 O, C 10 H 18 O, and C 10 H 20 O) increased suddenly during the disinfection events (10 −1 to 10 2 ppb) and exhibited volatility-dependent temporal emission profiles. VOC emission factors ranged from 10 0 to 10 4 μg g −1 , and thymol intake fractions ranged from 6 to 7 × 10 3 ppm. Rapid new particle formation events were observed due to ozonolysis of monoterpenes and monoterpenoids, increasing sub-100 nm particle number concentrations by 10 4 to 10 5 cm −3 . Botanical disinfectant sprays initiated multiphase inhalation exposure to VOCs, secondary organic aerosol, and sub-10 μm droplets, with large deposited doses in each respiratory tract region associated with the latter two.
Clamped fiber Bragg grating (FBG) sensors have been widely applied in engineering strain measurements due to their advantages of high flexibility and efficiency. However, due to the existence of the interlayer, the strain measured by the encapsulated FBG sensor is not equal to the strain of the host material, which causes strain measurement errors. In this paper, the strain transfer analysis of a clamped FBG sensor based on the shear-lag theory is conducted to improve the accuracy of strain measurements. A novel theoretical model for the axial strain distribution of a clamped FBG sensor is proposed. It is also discussed how the gauge ratio and interlayer thickness affect the strain transfer rate. The accuracy of the proposed theoretical model is verified by experimental tensile tests. The theoretical value of the strain transfer rate matches well with the tested value.
We conducted an experimental case study to demonstrate the application of proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) for mobile breathing zone (BZ) monitoring of volatile chemical exposures in workplace environments during COVID-19 disinfection activities. The experiments were conducted in an architectural engineering laboratory—the Purdue zero Energy Design Guidance for Engineers (zEDGE) Tiny House, which served as a simulated workplace environment. Controlled disinfection activities were carried out on impermeable high-touch indoor surfaces, including the entry door, kitchen countertop, toilet bowl, bathroom sink, and shower. Worker inhalation exposure to volatile organic compounds (VOCs) was evaluated by attaching the PTR-TOF-MS sampling line to the researcher’s BZ while the disinfection activity was carried out throughout the entire building. The results demonstrate that significant spatiotemporal variations in VOC concentrations can occur in the worker’s BZ during multi-surface disinfection events. Application of high-resolution monitoring techniques, such as PTR-TOF-MS, are needed to advance characterization of worker exposures towards the development of appropriate mitigation strategies for volatile disinfectant chemicals.
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