One thing that would help a lot would be to dramatically improve ventilation in indoor spaces. What makes outdoor spaces safer is that air does not linger. A

One thing that would help a lot would be to dramatically improve ventilation in indoor spaces. What makes outdoor spaces safer is that air does not linger. A few options seem possible: 1. Weather and building permitting, open all of the windows. 2. Install a high efficiency filter (Probably MERV 14 or better is needed). This probably requires upgrading blower fans in the HVAC system. 3. Install the highest MERV filter that the system can support, and supplement this with a UV-C disinfection system inside the air handler. In general you need pretty powerful UV-C lights in the air handler to destroy viruses as they're passing through the system, but these are commercially available (https://www.johnsoncontrols.com/-/media/jci/be/united-states/airside-systems/air-handling-units/files/be_appguide_uvclight_ahu.pdf https://www.johnsoncontrols.com/-/media/jci/be/united-states...) 4. Bring in more fresh air, possibly by changing HVAC settings, possibly install a contraflow heat exchanger to recover heat/cooling as air is exchanged. 5. Install portable HEPA type filters. You will need a lot.