On the left in the photo is a new filter for our AC/furnace; on the right, one about 60-75 days old including two weeks of wildfires. This is, of course, used inside the house, so everything here has come inside though we've had the doors and closed almost all of the time for the past couple of weeks.
These are MERV 13 filters (which our landlord is paying for! Thanks!) Two technicians from Blake's said that a filter of this high value is suitable for our fairly modern HVAC. These are what's planned for use at Lincoln40. When they get this black and clogged up they also start to whistle a bit in the holder as air is trying to go around them, which at least raises energy costs.
Some of this black crap would be circulating back into the house if we were using a standard MERV 8 filter, but with microparticulates it's actually the stuff that you can't see that's the most dangerous. MERV 13 filters help with this, taking out 75% or less of 0.3 to 1.0 micron particles. MERV 8 filters are not even rated for taking out the better known 2.5 micron particles.
Every HVAC system in town that can handle this should be equipped with them. I would suggest running anytime if just on filter setting anytime PM 2.5 is not "Good".
Stand alone HEPA filters remove a lot more pollution, but can be both expensive and energy-intensive. Use them if you can, at least when the air is at its worst.
(Keep in mind that everything very tiny that settles to the floor or carpet gets turbo-distributed by a non-HEPA, non-sealed system vacuum cleaner.)
So... hey Davis landlords! Would you accept a level-playing field requirement that all rental units should have the best furnace filters possible within the capabilities of their HVAC system?
Healthy tenants pay rent more reliably, right?
Todd Edelman is a resident of Birch and a member of the Bicycling, Transportation and Street Safety Commission (for identification purposes only)