Living with smoke…

Smoke in the Methow Valley, Sept. 8, 2022: 600 ug per m3 = Hazardous air. At this level, the ug/m3 and AQI are nearly the same at 600.

Anyone living in the west knows that smoke is now a common occurence almost every summer. It doesn’t seem to matter where you live, although California and the NW states seem to get it the worst. While I was hoping to finish my hike of the Pacific Crest Trail (PCT) in early September, fires near the WA-British Columbia border exploded and the PCT has been closed since late August. I took this picture on September 8th, 2022, near Mazama WA. Although I have been doing research on smoke and air quality for 2 decades, this was the worst smoke I have experienced. (I did once see similar pollution levels from a Russian factory back in 1989!). Fortunately this horrible smoke only lasted a day or so here. But when the pollution is this high, I do not reccomend going outside without an N95 mask. I spent most of this day indoors.

But if you have read my previous blog posts, for example this one:, you know that being indoors is no guarantee of good air. In fact, if there is smoke outside, your air inside will be bad unless you take active steps to keep smoke out and filter your indoor air.

So having now dealt with smoke and high concentrations of particulate matter in WA state for the last 8 years or so (since at least 2015), I thought it would be useful to summarize some of the main tools I use during the smoke season.

  1. You have to know what is coming. The best tool I have found is the NOAA HRRR forecast model. I wont go into all the details about this tool, but lets just say it is hands down the best out there to predict where smoke will travel in the next few days:
Image from the NOAA HRRR smoke forecast model. Note that time is in UTC or Greenwich Mean Time. Here in Washington state, UTC is 7 or 8 hours behind UTC. (7 hours when we are daylight saving time, 8 hours when we are on standard time)

2. You have to know what is happening right now. There are two good tools, one is the EPA fire and smoke map and the other is the Purple Air map:

AirNow fire and smoke map with the smoke plumes shown.
AirNow fire and smoke map for the same date as above. Sometimes the smoke plumes make it hard to see the sites. So its good that you can remove them from the image.

The advantage of the EPA fire and smoke map is that you can see both the official air quality sites, plus the Purple Air sites and you can see fire locations and satellite derived smoke plumes. One disadvantage is that becase this site has a detailed set of criteria for inclusion of the Purple Air data, many Purple Air sites are not shown.

The Purple Air map includes all sites with PA sensors, including indoor sites (indicated by a black circle). So this is where you will see how well you are doing at keeping smoke out of your house! Very important. If you are interested in details about smoke in your neighborhood, this is a more useful than the EPA site, which omits many sites. But when you look at the PA map, be sure to apply the correction factor to the data. Choose

Purple Air sensor map. Be sure to apply a correction to the raw PA data.
While all of the corrections give similar results, for consistency with the official data, choose US EPA for the correction. If you want the values in AQI, click on the box above the correction and you can select that.

It is useful to understand the difference between Air Quality Index (AQI) and the actual concentrations, usually in micrograms of particulate matter less than 2.5 micron diameters. (PM2.5). For most non-technical folks, using the AQI is a bit simpler. Here is a guide from the EPA about how to interpret the AQI values:

3. Finally, you need tools to know whats going on inside your home or apartment and active tools (fans, filters) to filter smoke out. At minimum, I reccomend that every home have at least two standard 20 inch box fans with 20 inch MERV-13. This will only cost about 60 bucks and it will reallly improve the smoke situation inside your home. Why two? Well depending on the size of your house, number of rooms, etc. I generally keep one running in the main living area and one in a bedroom. Or get three if you more bedrooms/kids. You get the idea. If you want to spend a bit more money, you can buy standard air purifiers and these are much quieter, but the fan/filter combination seems to work just as well. The air purifiers run 100-300 bucks each (at least) and you really need more than one. I also think its very helpful to have an indoor air quality monitor, such as a Purple Air sensor. The indoor units are less than 200 bucks. But if you dont want to buy one of these, then when the smoke comes, just close your windows and turn on your fans with MERV-13 filters and you will reduce your indoor particulate concentrations to reasonable levels. If you are a science geek (like me), you really want to see those numbers!

So I hope this guide is useful. At this point, we are now living with climate change. Smoke is one clear example of that and everyone in the west should be prepared. There are other things to think about with climate preparation that we should consider, such as flooding, heat risk, etc. And there are concrete steps we can all do to reduce our emissions and therefore our impact on climate But I’ll leave those topics to a future blog post. For now, be well, keep cool and keep the smoke out ! dj

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