Real-time measurements of fluorescent aerosol particles in a living laboratory office under variable human occupancy and ventilation conditions

Abstract

The abundance of super-micron biological and abiotic particles in occupied indoor environments can be influenced by time-dependent changes in human-associated emissions and building ventilation conditions. Real-time measurements of fluorescent aerosol particles (FAPs) were integrated with a building sensing platform to evaluate the influence of human occupancy and ventilation on the temporal dynamics of fluorescent biological and abiotic particles in a living laboratory office. Concentrations and size distributions of FAPs were measured via laser-induced fluorescence (LIF). Human occupants were identified as a major source of super-micron FAPs in mechanically ventilated office buildings. Mass concentrations and size distributions of FAPs larger than 3 μm scaled with human occupancy in the office. Detailed single particle fluorescence data indicated that human-associated emissions enriched the office atmosphere with specific FAP types that varied in morphology. Office occupants were strong emitters of ABC-type particles (number and mass), and to a lesser extent, A-type particles (number and mass), AB-type particles (mass), and B-type particles (mass). Such FAP types are related to common indoor bacterial and fungal aerosols and fluorescent clothing fabric fibers. The introduction of natural ventilation via a double skin glass façade increased the indoor abundance of FAPs due to the efficient transport of outdoor FAPs into the office. While LIF provides valuable real-time data on indoor FAP dynamics, it lacks specificity and cannot fully resolve the origins of fluorescent biological and abiotic particles in indoor spaces.