Aerosol dispersion in multi-patient hospital rooms
Airborne transmission of disease is of concern in many indoor spaces. Here, aerosol dispersion and removal in an unoccupied 4-bed hospital room was characterized using a transient aerosol tracer experiment for 38 experiments covering 4 configurations of air purifiers and 3 configurations of curtains. NaCl particle (mass mean aerodynamic diameter ∼ 3μm) concentrations were measured around the room following an aerosol release. Particle transport across the room was 1.5 – 4 minutes which overlaps with the characteristic times for significant viral deactivation and gravitational settling of larger particles. Concentrations were close to spatially uniform except very near the source. Curtains resulted in a modest increase in delay and decay times, less so when combined with purifiers. The aerosol decay rate was in most cases higher than expected from the clean air delivery rate, but the reduction in steady-state concentrations resulting from air purifiers was less than suggested by the decay rates. Apparently a substantial (and configuration-dependent) fraction of the aerosol is removed immediately and this effect is not captured by the decay rate. Overall, the combination of curtains and purifiers is likely to reduce disease transmission in multipatient hospital rooms.
Indoor fate of fragrances
Fragrances from personal care products are important sources of volatile organic compounds. We aim to fundamentally understand what happens to these molecules when they are emitted into the indoor atmosphere. Four key questions govern our research. These questions are: (1) how fast are the molecules oxidized?, (2) what are their oxidation products?, (3) what is the mechanism of transformation of the molecules of interest?, and ultimately (4) how are these molecules transformed and by what key oxidants? The key instrument used to effectively tackle all four questions is our online proton-transfer-reaction time-of-flight mass spectrometer.
Indoor oxidants from cooking aerosols
Cooking is a major source of indoor brown carbon. Brown carbon, in addition to light source, ground state molecular oxygen, and water can lead to the formation of singlet oxygen. Singlet oxygen is the first excited state of oxygen and can be a competitive oxidant indoors, if produced. We aim to identify what cooking events lead to higher amounts of brown carbon production. Our goal is to investigate whether these cooking organic aerosols absorb indoor light to initiate photochemistry that can lead to the production of singlet oxygen indoors.