Iron Tongue

I run 2 air filters 24/7. Change the filters as often as you see fit. Whether you trust the "change now" indicator or not, the filter is constantly decreasing in efficiency due to clogging and you may not wish it to reach the point of full saturation before changing. Even if you are getting low readings, the filter decreases in efficiency with each hour of operation and the charcoal is not be as effective as when new, so enough smells and other microparticles may be getting through to bother you, even past a hepafilter. And "NO" exposing charcoal to sun