Thread by @marinavance

We have a newly published paper on #IndoorAirQuality and it is #OpenAccess! This was a fun study and here’s a short thread on some of our findings. /1
pubs.rsc.org/en/content/art…

We put a bunch of low-cost air quality monitors in four homes to measure concentrations of fine particulate matter (PM2.5) during the occupants' everyday lives. Each home deployment was about 10-weeks long.

Not all low-cost monitors behaved the same way. Some were much better than others. But they all performed better during background periods (no indoor sources) compared to when there were indoor PM2.5 sources, such as indoor cooking. 3/

In times when indoor cooking activities released PM2.5, the low-cost air quality monitors overestimated concentrations by a factor of 1.6-2.2.
4/

This is not a big deal if you are using this as a consumer. The monitor will tell you that there are a lot of particles in air, so you need to get them out through ventilation or filtration. If you are using it for research, you need to figure out a good correction factor.
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Kitchen emissions reached the bedrooms almost instantly in smaller and open floor plan homes. In a home where bedroom doors were kept closed, it took about 45 min for the kitchen emissions to reach the bedroom.
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When those kitchen emissions reached the bedrooms, they were up to ~30% lower in concentration than in the kitchen.
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Particle concentrations go down bc:
1. they get diluted with indoor air as they travel through the home,
2. they get diluted with outdoor air that is always coming in,
3. because they adhere to surfaces as they travel.
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Two quick comments on this:
- Outdoor air is always coming in, no matter how airtight we think our home is. Unless your home is especially design to be super airtight.
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- Once a small PM2.5 particle adheres to a surface, it’s almost impossible for it to come off. This means that our walls are covered in deposited particles and organic films from years and years of indoor activity.
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We also put a good-quality portable air cleaner (PAC), with a nice HEPA filter, in these homes. For 3 weeks, the PAC was in the kitchen and for another 3 weeks it was in a bedroom. And for another 3 weeks, the PAC was not used.
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Using a PAC in the kitchen was more effective in reducing indoor PM2.5 exposure compared to putting it in the bedroom. This is bc outdoor air quality was generally good during this study, so most of the indoor PM2.5 came from cooking, not from infiltration from outdoors.
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One of the homes had a high-quality extracting range hood over the stove. It was used every time they cooked. The PAC didn’t do much benefit there. The range hood alone was sufficient to remove the cooking particles.
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My general advice coming from this work:
1. Using a low-cost PM2.5 monitor in your kitchen is a good idea! It will tell you when you need to ventilate because of cooking, other indoor activities, or infiltration from outdoor sources, like during wildfire season.
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2. Using a filtration portable air cleaner in your kitchen is a good idea if you don’t have a good extracting range hood. If outdoor levels get high (because of urban air pollution, haze/smog, or wildfires), then I’d recommend moving the PAC to the bedroom at nighttime.

{fin}

PS - I am not tagging the people who actually put in the most effort in this work because they are not on Twitter. PhD student Sumit Sankhyan and BS student Julia Witteman spent much effort & energy in this project for ~3 years and deserve much appreciation!