Thread by @wirecutter

(THREAD) During a wildfire, you’ll need to change your filters more often than you would under normal air conditions, and there are a few indicators that can help you know when it’s time to replace one. wrctr.co/2RMEbpa

According to an air quality engineer & filtration expert:

"If I lived near the wildfires & didn’t find the cost prohibitive, I’d probably change a 3-month filter every month during the season. Or possibly after each major event— say if a fire gets close enough to be a big deal."

Note that wildfire smoke is a complex mixture, incorporating both:

• physical smoke particles (which filters trap permanently)

&

• water vapor + volatile organic compounds (gases), which are not trapped—and the latter of which create the smoky scent

The wet particles + ones w/ gases adsorbed on them can be collected, then give off smells the next time the fan comes on

So if you feel like the air breathes easier+smells OK w/ the HVAC on but are gagging in the first few min the HVAC is on again, changing the filter could help

VISUAL CUES TO LOOK FOR:

Clogging increases the pressure differential b/w the intake & outflow sides, which causes a filter’s pleats to flatten OR its frame to buckle

Both signal that smoky air is finding a path around the clogged filter, & that it’s time to install a new one

Along w/ obvious steps like keeping windows & doors closed, we also advise shutting off bathroom fans & range hoods:

Both of these vent directly to the outside &, as a result, draw an equal volume of smoky outdoor air in through window frames & other leaky spots.

Also, consider adding a portable air purifier w/ a VOC filter

All our picks have them, & though in our tests against an extreme load of ethanol vapors we found most of them ineffective, anecdotally we can say they perform well under heavy smoke conditions wrctr.co/2ZUvMEm

Both in guide author Tim Heffernan’s apartment and in our New York test space, after running our top picks for a few hours, there was little olfactory evidence that hundreds of matches had been burned nearby. wrctr.co/2ZUvMEm

Lastly, Owen noted that the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) has begun working on building-filtration guidelines specific to wildfire conditions. We’ll be following up on this as it develops.

nytimes.com/wirecutter/rev…