Reducing the particles generated by flushing institutional toilets

Source avec lien : Journal of Occupational and Environmental Hygiene, (En ligne). 10.1080/15459624.2022.2053693

Les particules en suspension dans l’air jouent un rôle important dans la transmission du SRAS-CoV-2, le virus à l’origine du COVID-19. Une étude précédente a indiqué que les toilettes institutionnelles à chasse d’eau O-mètre (FOM) peuvent générer de 3 à 12 fois plus de gouttelettes que les autres toilettes par éclaboussure (grosses gouttelettes) et par éclatement de bulles (fines gouttelettes). Dans cette étude, un couvercle de suppression des aérosols a été évalué pour mesurer la réduction des particules par taille en utilisant trois paramètres : le nombre, la surface et les concentrations de masse.

Airborne particles play a significant role in the transmission of SARS-CoV-2, the virus that causes COVID-19. A previous study reported that institutional flush-O-meter (FOM) toilets can generate 3–12 times as many droplets as other toilets by splashing (large droplets) and bubble bursting (fine droplets). In this study, an aerosol suppression lid was evaluated to measure the reduction of particles by size using three metrics; number, surface area, and mass concentrations. To quantify toilet flush aerosol over time, detailed particle size distributions (from 0.016–19.81 µm across 152 size bins) were measured from a FOM toilet in a controlled-environment test chamber, without ventilation, with and without use of the suppression lid. Prior to each flushing trial, the toilet bowl water was seeded with 480 mL fluorescein at 10 mg/mL. A high-speed camera was used to record the large droplet movements after flushing. An ultraviolet-visible spectrophotometer was used to analyze the wipe samples to evaluate the contamination on the lid. The particle number, surface area, and mass concentrations without a lid were elevated compared to a lid in the first 90 sec. Overall, the lid reduced 48% of total number concentration, 76% of total surface area concentration, and 66% of total mass concentration, respectively. Depending on the particle size, the number concentration reduction percentage ranged from 48–100% for particles larger than 0.1 µm. Large droplets created by splashing were captured by the high-speed camera. Similar studies can be used for future particle aerodynamic studies. The fluorescein droplets deposited on the lid back sections, which were closer to the FOM accounted for 82% of the total fluorescein. Based on two-way ANOVA analysis, there were significant differences among both the experimental flushes (p = 0.0185) and the sections on the lid (p = 0.0146). Future work should explore the aerosolization produced by flushing and the performance of the lid in real restroom environments, where feces and urine exist in the bowl water and the indoor ventilation system is in operation.

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