Out, out damn smoke!

Starting in mid-August, smoke was affecting a large chunk of the country.  There are hundreds of fires burning right now, with large fires being reported in: Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. Currently the National Interagency Fire Center (www.nifc.org) is reporting 4.7 million acres burned as of 9/8/2020 for wildland fires, so it looks like 2020 is on its way to another huge fire season. Note that I avoid saying “wildfires”, as this term is rather vague. A fire can be ignited on “wildlands” (forests, prairies, ranges, etc.) for many reasons (campfires, lightning, etc.).  The term “wildfire” implies that it was a natural fire, but this is often not the case. I’ll discuss this in a future blog post and the relationship of fires to climate change. But let’s get back to air quality…. 

Here is the current fire and smoke map for September 9th, 2020. Smoke plumes are identified from various satellite products. Note that smoke detected by a satellite, tells us the smoke is present overhead, but does not necessarily tell us the smoke is at the ground level. For this we need the surface measurements.

US Map of current fire and smoke on Sept 9, 2020 showing the western US Coast and inland areas on fire.
U.S. map of current fire and smoke on Sept. 9, 2020

Here are the air quality maps for August 21st and September 8th.     

Air quality map showing poor quality over California NE through Montana
AQI map for Aug. 21, 2020 
Air quality map showing poor quality over California North through Vancouver BC
AQI map for Sept. 8, 2020 

Concentrations of PM2.5 (particles with diameters less than 2.5 microns) and O3 have exceeded the health thresholds around much of the country, especially the western U.S. The maps above show the air quality using the EPA’s Air Quality Index (AQI). 

Air Quality Index levels with corresponding health concerns Green is good up to Hazardous levels for everyone.
Air Quality Index levels with corresponding health concerns

Now that the smoke has arrived to the Puget Sound region, where I live, I’ve spent a lot of time in the last few days trying to keep the smoke out of my house and figuring what works best. I’ve reconfigured a 20” box fan and pulled out a box of MERV-13 filters that I’ve had under my bed since the last time we got a big smoke event (2018). I used a similar process as what’s on the Puget Sound Clean Air Agency’s website:  https://www.pscleanair.gov/525/DIY-Air-Filter

Only mine was even simpler!  The only tool I used was some duct tape (aka duck tape!). Here is a picture of my do- it-yourself air purifier with a MERV-13 filter attached. Make sure you put the filter on the inlet side of the fan and follow the arrow on the filter for the airflow.   

do- it-yourself air purifier with a MERV-13 filter attached on the backside of the fan (air entry side).
Do-it-yourself air purifier

I had all the materials ready to go after the smoke events here in 2018, but didn’t have a chance to use them to try them out til this past Monday night.  When the smoke came into the Puget Sound region, I jumped into action. I pulled out my duct tape and got my first filter ready to go. I was watching a movie that evening and when I got ready for bed, I noticed my upstairs smelled strongly of smoke. So I decided to move downstairs into the guest bedroom and fight to keep out the smoke. I also have two low-cost particle sensors in my house. At first they were both in the same room (kitchen-dining room area). But about 10 pm on Monday, I moved them on to the guest bedroom to monitor how well my filter was doing. Here is some data: 

Dr. Jaffe's home air quality sensors reporting difference between outside, dining room, and guest room with DIY filter. Guest room was the lowest.
Dr. Jaffe’s home air quality sensors reporting difference between outside, dining room, and guest room with DIY filter

This shows that the smoke arrived to Puget Sound around 8 pm and up until about 10 pm, the two air quality sensors in my house were climbing fast and showing identical values. But when I moved one into the guest room, its values starting dropping due to the fan/filter combination. Over the course of the night, the values stayed relatively low, while outside the air quality was poor and also in other rooms of my home.  

But there is an important point I left out, if you go back to my other post on indoor air quality: https://sciencenorthwest.com/how-to-keep-your-home-smoke-free-during-wildfire-season there is a chart on MERV-13 specs. Notice that while MERV-13 should filter 90+% of the 1-3 um (micron) particles, its not clear how much of the smaller particles are removed. This is really important as most smoke particles are these smaller ones, below 1 um in diameter. So we better make sure the MERV-13s are taking these buggers out!     

So I tested this with a particle counter that counts the particles by size.    Here are the results. This compares the # particles that were outside at 10 am on 9/8/2020 with the number that were inside my guest bedroom with the MERV-13: 

Number of particles that were outside at 10 am on 9/8/2020 with the number that were inside my guest bedroom with the MERV-13 

The instrument I used (called an “Optical particle counter”) can’t count particles smaller than 0.3 um, but still, we can feel pretty good about the ability of the MERV-13 to remove all of the key particles in smoke.

We had a bunch of press for our work on indoor air quality. If you are interested, you can see the reports here: 

THE UPSTAIRS OF MY HOUSE SMELLED LIKE CAMPFIRE 
KIRO7, Sept. 8, 2020 

Expert advice to stay healthy and safe from wildfire smoke 
Q13fox.com, Sept. 8, 2020 

How to protect yourself from smoky air 
KOMO Radio, Sept. 8, 2020 

Now see the next post for our cartoon for the week to go with this story.  But it needs a caption! 

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