As in many other areas we’ve been having a lot of wildfires (grassfires mostly) where I live in the last couple of months. Thankfully the fires are not close to my house, but every day we get a strong smell of smoke that causes coughing and sore throats, and sometimes a visible haze in the air.
I’ve started closing the doors and windows when the smell of smoke starts, and turning on the air purifiers (Sqair with carbon filter). However I have noticed that they don’t really reduce the smell of smoke.
I recently bought a QingPing Gen 2 (on Ethan’s advice, thanks Ethan!) so I could get some data about what was actually happening, and when the smoke smell comes, both VOCs and PM 2.5 rise. When I run the air purifiers PM 2.5 goes down very low but the VOCs level is pretty much unchanged. (I know the VOCs measurement on this monitor is relative.)
I thought the carbon filter on my Sqair would help with VOCs but it appears not to be the case. I know there are a lot of different VOCs so I expect this is part of the puzzle.
My questions are:
What type of air purification works for wildfire smoke?
What gases / other compounds are generally in wildfire smoke?
Thanks for joining the forum! It’s nice to have you here.
I think there may be a few factors at play here. As you’ve already noted, the PM2.5 is decreasing (implying that the mechanical filtration layer is working), but the VOC level and odours aren’t decreasing noticeably or, in the case of odours, are still present. I believe this may be a physical limitation of the carbon filter on the Sqair as it’s not very deep.
Gas adsorption needs contact time, and at the velocities the Sqair is sending gas through the filter, the contact time is likely too low leading to low single-pass removal rates. If the filter is older, it’s likely already at its adsorption capacity, which would make the issue even more severe.
Unfortunately, I think a gas-phase air purifier would likely be needed in a situation like this.
With that said, it’s likely that there is some decrease in VOCs (unless new, outdoor air is being introduced at a similar rate) and the SGP40 in the Qingping simply can’t identify the change as it’s slow enough that it’s hidden by the changing baseline.
With that said, the smell itself often comes from gases with odour thresholds in the low ppb. Therefore, the smell can remain and it’s not a good proxy for health risk (a lot of which is driven by PM2.5, which you are already filtering).
Please let me know if you have any further questions!
