A guide to dealing with air pollution in Seattle, SF, Vancouver, and other west coast cities


I first wrote this as a google doc in response to the horrendous air pollution/smoke in Seattle/Vancouver in August 2018.

2-minute Summary:

  • Increased air pollution in <your city> caused by forest fires near <your city>.
  • The primary health concern is the particulate matter, especially PM2.5 — these particles are so small that they can enter your bloodstream directly.
  • The simple not-too-expensive steps to take to counter its effects:
    – Monitor outdoor PM2.5 levels using an app such as Airvisual or Plume, which source from government data sources
    – Wear a N95+ mask outside when PM2.5 surpasses 25 μg/m3 (10 μg/m3 if you want to be conservative)
    – Use a purifier home that uses a HEPA filter.
    1. Good but expensive option (don’t use auto mode). ($200)
    2. Cheap DIY option ($25)
    3. Slightly better DIY option ($40)
  • Eat more broccoli, Brussel sprouts, or cauliflower — they can counteract pollution
  • Extra geek out (not necessary, but useful if you’d like more data):
    – Buy an Airvisual Pro, which IMO is the best indoor consumer-grade air sensor out there ($250)
    – Or Buy a Plume Flow, probably the best portable consumer-grade air sensor out there ($200)

What’s happening? What is bad about this air pollution?

If you’re reading this, you probably know what’s happening. Wildfires in Washington State + British Columbia have led to Seattle, Portland, and Vancouver being blanketed in smoke on and off for the past few weeks.

How to deal with particulate matter- masks and HEPA filters

Fortunately, there are some easy ways to deal with PM2.5 and PM10 pollution:

1. Wear a mask when outdoors

I recommend this 3M N95 mask ($20 for a 10 pack on Amazon). Make sure to fit it properly (note this video shows a valveless model, but the same fit instructions apply). Here’s another way to check if your mask fits properly**.

  • Some tests show that they can block a lot more particles (99%) for a lot cheaper than more expensive masks (see article here)
  • It’s cheap at $2 each.

2. Get a Hepa-rated purifier indoors

Get one of these air purifiers. Most of these are rated for ~500 sq.ft. so make sure to get enough, or worse case, just run it in your bedroom at night.

a) Cheapest option: make your own DIY fan with a HEPA filter and a box fan. ~$20, 10minutes since you probably already have a box fan

Take a HEPA filter rated MERV 12 or higher (I recommend this one from 3M or this one, which is recommended by Wirecutter)

b) Cheaper option: slightly higher tech DIY option: $40, ~30minutes:


c) Out of box option: expensive non-DIY air filter ($200, 5min setup time)

I trust the wirecutter’s recommendation of the Coway AP-1512HH.

  1. The fan is designed with the load of a filter in mind- no fire risk
  2. It has a carbon filter for gas pollutants, although the it’s unclear the thickness of the carbon filter is enough to filter much out (see wirecutter article)

d) option most Seattle-ites won’t have

Most Seattle homes don’t have central HVAC, so it’s not an option, but you could try using an option like this: https://thewirecutter.com/reviews/furnace-and-air-conditioner-filters-we-would-buy/

e) Do I need to buy a sensor myself? As a review, the basic strategy with steps 2a-d is to rely on outdoor sensor data provided by the government via Airvisual or Plume, then run your filters when the PM2.5 levels get above 10 μg/m3

This isn’t quite right, since indoor air usually has lower PM (although not an order of magnitude) than outdoor air even without filtering.

3. Eat more Broccoli, Brussel sprouts, cauliflower

This article has it all: https://smartairfilters.com/en/blog/eating-broccoli-protects-air-pollution/

4. Get some eye drops for your eyes

My eyes have been stingy slightly the last few weeks (normally never do), so I called up my eye doc and asked what I could do.


Further resources/more reading

I’ll add more to this doc as time passes (please comment if you’re wondering about something), but if you want to do further reading, here are a few resources I recommend:

Complete medical legal disclaimer

The information contained in these topics is not intended nor implied to be a substitute for professional medical advice, it is provided for educational purposes only.



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Steven Zhang

Steven Zhang


Essays about random lifehack topics here. More writing about factories, climate, faith communities at: stevenzhang.com