Abstract
Abstract. This study presents the first reference calibrations of three commercially available bioaerosol detectors. The Droplet Measurement Technologies WIBS-NEO (new version of the wideband integrated bioaerosol spectrometer), Plair Rapid-E, and Swisens Poleno were compared with a primary standard for particle number concentrations at the Federal Institute for Metrology (METAS). Polystyrene (PSL) spheres were used to assess absolute particle counts for diameters from 0.5 to 10 µm. For the three devices, counting efficiency was found to be strongly dependent on particle size. The results confirm the expected detection range for which the instruments were designed. While the WIBS-NEO achieves its highest efficiency with smaller particles, e.g. 90 % for 0.9 µm diameter, the Plair Rapid-E performs best for larger particles, with an efficiency of 58 % for particles with a diameter of 10 µm. The Swisens Poleno is also designed for larger particles but operates well from 2 µm. However, the exact counting efficiency of the Poleno could not be evaluated as the cut-off diameter range of the integrated concentrator unit was not completely covered. In further experiments, three different types of fluorescent particles were tested to investigate the fluorescent detection capabilities of the Plair Rapid-E and the Swisens Poleno. Both instruments showed good agreement with the reference data. While the challenge to produce known concentrations of larger particles above 10 µm or even fresh pollen particles remains, the approach presented in this paper provides a potential standardised validation method that can be used to assess counting efficiency and fluorescence measurements of automatic bioaerosol monitoring devices.
Highlights
Routine pollen monitoring is carried out across the world, in developed countries, where the prevalence of allergies is highest (Wüthrich et al, 1995; Ring et al, 2001; D’Amato et al, 2007; Buters et al, 2018)
To test the Swisens Poleno device at lower concentrations, the PSL number concentration in the aerosol homogeniser was set to about 1 cm−3; the reference particle counter measured the undiluted aerosol at 1 cm−3 to ensure enough particles were counted for statistical analysis, while the Poleno device, which has a much higher sampling flow rate, sampled the diluted aerosol flow
Note that for the calculation of the reference concentration, Cref, the aerosol flow sampled by the reference optical particle counter (OPC) is always converted to volumetric flow at ambient temperature and pressure (23 ± 2 ◦C and 960 ± 10 hPa)
Summary
Routine pollen monitoring is carried out across the world, in developed countries, where the prevalence of allergies is highest (Wüthrich et al, 1995; Ring et al, 2001; D’Amato et al, 2007; Buters et al, 2018). Two more recently developed instruments based on airflow cytometry, the Plair Rapid-E (Kiselev et al, 2013; Crouzy et al, 2016; Šauliene et al, 2019) and Swisens Poleno (Sauvageat et al, 2020), have shown the potential to classify pollen taxa This is an essential requirement for pollen monitoring since allergy sufferers, one of the main end user groups of the information these networks provide, are sensitive to specific pollen taxa above particular concentration thresholds (Jaeger, 2006). As interest grows in using automatic instruments to provide real-time information about airborne pollen concentrations, it is vital that standard calibration methods are developed that can be applied across monitoring networks.
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