A Field Pilot Study of the Aero Quattro Air Purifier Operated Directly on the Air Ventilation of A Navigating Cruise Ship: Effect on New Particle Formation and Effectiveness Against the Airborne Phi6 Model Virus

Effective control of airborne virus transmission is essential for preventing the spread of infection and mitigating health risks. Cruise ships are one of the public indoor spaces where SARS-CoV-2 infections have been significant, leading to extended quarantines. Commercial Air purifiers are available; however, depending on their technology, some are efficient at neutralising viruses, but at the same time, they can induce the production of ultrafine aerosol particles, which could be potentially harmful to health. In contrast, others might be less efficient in neutralising viruses, but do not trigger the formation of ultrafine particles. This pilot field study investigates, in real operational conditions, a commercially available air purifier (Airforte Ltd, Aero Quattro) directly integrated into the air ventilation system on board the cruise ship Viking Grace, which cruises between Turku, Finland, and Stockholm, Sweden, during 2022. The patented Aero Quattro air cleaning technology used in this pilot study comprises an active ionisation, two UV-C lights and two photocatalytic honeycomb-type flow laminar systems. The ultrafine aerosol particle size distribution and total aerosol particle concentration were measured online, allowing the measurement of ultrafine particle formation, if any. A non-pathogenic Phi6 surrogate virus was used to simulate the spread of SARS-CoV-2. Viable Phi6 viruses were nebulised inside the air ventilation system, passed through the Aero Quattro, and finally collected using biosampler, to then be offline analysed in the laboratory back on land. We demonstrate that under realistic operation conditions, the Aero Quattro, 1) does not induce the formation of ultrafine particles, 2) successfully eradicates the live Phi6 surrogate viruses within the detection limit. Although this pilot study was performed on a cruise ship air ventilation system under nominal operating conditions, integrating such an air purification system into various air ventilation systems could help restrain virus propagation in different public areas