FWIW, Open Air Treatment was used to fight the 1918 flu pandemic. But I think culturally, we (Americans at least) love our HVAC. "A combination of fresh air, s

FWIW, Open Air Treatment was used to fight the 1918 flu pandemic. But I think culturally, we (Americans at least) love our HVAC. "A combination of fresh air, sunlight, scrupulous standards of hygiene, and reusable face masks appears to have substantially reduced deaths among some patients and infections among medical staff. " https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504358/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504358/