It could be Ozone. Possibly harmful for human depending on concentration but sometimes used for human. EPA says that just HEPA filter is enough to catch covid,

It could be Ozone. Possibly harmful for human depending on concentration but sometimes used for human. EPA says that just HEPA filter is enough to catch covid, so it seems that there are less chance to upsell filter only. Selling more appliances would be good. https://www.epa.gov/coronavirus/air-cleaners-hvac-filters-and-coronavirus-covid-19 https://www.epa.gov/coronavirus/air-cleaners-hvac-filters-an...