Real-time monitoring of bioaerosols (e.g., bacteria, fungi, virus aerosols) is attracting more attention since the COVID-19 outbreak. Rapid-E+ was developed in 2020 by Plair to extend the capabilities of Rapid-E (old version) in monitoring large bioaerosols such as pollen to small bioaerosols like bacteria and fungi with diameters down to 0.3 µm. Rapid-E+ measures (1) aerodynamic diameters of bioaerosols, (2) the 2D Mie scattering images to have the full details on particle morphology, (3) timely resolved, polarization and angle dependent Mie patterns, (4) fluorescence spectra resolved over 16 channels, and (5) fluorescence lifetime. These information of each single bioaerosol can then be analysed using artificial intelligence (machine learning). We present results of Rapid-E+ testing for classification of bacteria and fungi in confined environment. All detected bioaerosols were analysed based on Rapid-E+’s fluorescence and light scattering information. Firstly, they were analysed with a smart filter block to distinguish non-microbial particles. Secondly (“Classification Algorithm”), the filtered particles were further verified to be microbes, based on the calibration data step. Microbes were aerosolized in a bioaerosol chamber for Rapid-E+ training, and then for testing under different concentrations. Afterwards, we used several steps to classify and identify microbes. We used Bacillus subtilis to represent bacteria and Penicillium chrysogenum to represent fungal spores. Rapid-E+ enabled identification precision of 99% against background. For further distinguishment of bacteria from fungal spores, the achieved precision was 87% and 89% respectively. The real-time monitoring and classification by Rapid-E+ was also demonstrated by aerosolizing various concentrations of microbes again in the chamber. Pollen grains and pollen fragments can be detected by Rapid-E+ with similar or even better performance compared to the old version. Proprietary algorithms can be further developed by the user to extend the instrument application on specific microorganisms such as virus aerosol identification.

Rapid-E+: A smart platform for real-time monitoring of airborne bioaerosols in indoor and outdoor environment

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