3 ms·

> most commercial spaces and public buildings (like schools) already have HVAC systems incorporating HEPA filters (as good or better than N95 masks). So, here'

> most commercial spaces and public buildings (like schools) already have HVAC systems incorporating HEPA filters (as good or better than N95 masks). So, here's some anecdata. I have a PM2.5 sensor; not a great one, but good enough to measure relative changes. After buying an air purifier the PM2.5 count in our house dropped dramatically and consistently. Whereas the lower end before was a "2", now it reaches to "0"; I'd never seen the sensor register 0 before this. And the spikes from cooking are quickly scrubbed, whereas before they would cause a lingering increase in PM2.5 for the rest of the night. Even though I spend extra to get the higher grade filters for our HVAC, an air purifier still seems to have objectively improved the air quality far beyond what our HVAC was doing. In other words, I'm not sure an HVAC is a good replacement.

mensetmanusman 6y ago
This, it is amazing how long small particles linger. It’s like looking in a sun beam and seeing floating fibers near the couch. A very fun experiment to show children is to use a green laser pointer near a carpet floor so it is floating across the floor a couple inches. Then have the children hit the carpet around the beam and the beam will suddenly appear as the light scatters from the micron-sized dust particles. You can see how long it takes them to resettle, and point the laser anywhere to count a crude interaction/second with the light beam to get a sense of how dirty the air is (laser light volume is quite small :))
clairity 6y ago
that could be, but i'd note that a 2->0 PM2.5 count drop is likely not material to health as opposed to, say, a 20->2 drop. and furthermore, the time-averaged PM2.5 count while home is more relevant than the minimum absolute value.