I know at least the Ecobee can run the HVAC fan for a fixed period of time per hour. Not an expert on this but from what I know, I wouldn't approach it this wa

I know at least the Ecobee can run the HVAC fan for a fixed period of time per hour. Not an expert on this but from what I know, I wouldn't approach it this way. Even with a leaky house, the fan is mostly going to be blowing the air around the house, not pushing it out and sucking in fresh air which is what you want, and it will consume a lot of power doing it while shortening the life of an expensive part. Might help dilute a hot spot, but it's not creating a "stream" of air from the inside to out, it's just blasting the particles all over the place. You really do need to have a lower power fan that's actually able to push air directly outside, such as a bathroom fan or a stove vent. If you were going for a "quick hack", I would just use the bathroom fan for this purpose, but as mentioned above they're not designed for continuous operation and usually haven't been cleaned out in ages, so I would clean it out and try not to have it running when I'm not around in case it fails. For just filtering air vs ventilation, I read some stuff on filtering using a furnace filter, but in order to filter virus particles you need a very good filter (MERV-13), and almost no older furnace fans are designed for this, so this is a really good way to wreck your fan by making it work too hard. If you went this way, I would just buy a cheap fan from the hardware store and duct tape a MERV-13 filter onto it. Going to be a lot cheaper to replace that fan.