Why Doesn't My PA-II Detect Wood Smoke?

Or maybe it does and I’m just not looking at the right data? Recently our neighbor started using a meat smoker with mesquite wood and I was hoping to detect when he fires it up so we can close (or not open) those side windows.

In two cases so far, neither the PM2.5 nor PM10 showed any real change.

Any guidance would be much appreciated.

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Not sure I can help specifically in your case, without knowing more details. But I can confirm that my PA-II definitely detects woodsmoke, in both PM2.5 and PM10. Unfortunately, my neighbor heats with wood, and sends my meter skyward when doing that, and wind is out of his direction, or worse “light and variable” (since it just lingers, after the burning is done). As implied, wind direction can make all the difference - I’ll detect a neighbors BBQ easily, when wind out of their direction. But nothing, if not.

Thanks for the reply. A bit more details. We live in a neighborhood that’s in a valley and we are at the far South end of the valley. Think of the end of the valley almost like a canyon. We may actually have two problem sources but they both appear to be wood smoke. The meat smoker is slightly lower on the hill but in direct line with the wind coming down the valley. The other source is either a wood BBQ or more likely, a fire-pit further up the hill. Again upwind from us. The smoke smell “settles” in and around our house and that’s what I’m trying to detect. I’m just not seeing any real change in readings but we sure can smell the smoke.

Maybe instead of using the API and polling every 10 mins, I should poll the sensor locally at a much faster rate. Do you think that would help?

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If you can smell it, the meter will detect it.

I would get it registered on the purple air map, and you can view it there to begin with. I’m not doing any sort of API/polling (although I’m sure others are). Maybe once you see it on via purpleair map, to confirm the meter is working, you can put more work into API/polling. There’s way to see it quicker/more direct than the map too, with links, once you get it working there.

Good luck. Then the question becomes what to do, if the meter confirms what you’re smelling.

I would expect the same but that doesn’t seem to be the case.

Our sensor has been on the map working for over two years. I poll the data regularly and display it on a dashboard with other useful data.

I found another sensor about 1 mile North of us, at the other end of the canyon, so I’ve started polling that sensor and logging all of the readings for both sensors to an influxdb. So far both sensors are tracking each other with our sensor reading about 10-12 AQI higher. By tracking I mean the bumps and dips in the graph align for both sensors.

Let’s see what it shows the next time the wood smoke starts up.

BTW, I ordered the BME680 VOC upgrade to see if that might provide any additional data.

I also suffer from a neighbour’s wood smoke in Winter and can also confirm that my PA-II sensor picks it up. We see some pretty horrendous PM2.5 raw values especially at night during the winter months when they are using their chimney. Also if we ever have a barbecue (very rarely) the PM2.5 values go through the roof.

As for PM10 values, I never have personally relied on these readings from the PA-II, I think independent testing has shown that the Plantower sensors used are a lot more accurate for PM2.5 than PM10 (PM10 I believe is typically underestimated - though Purpleair would be be able to confirm). Having a more accurate PM10 value would be a great enhancement, especially in areas where there are a lot of atmospheric dust episodes (e.g. southern Europe from the Sahara) but for wood smoke I think the PM2.5 values are more important.

Thanks for the confirmation. I’ve started saving readings into an influxdb and graphing them with Grafana. So far our PA-II is tracking another sensor about 7/8ths of a mile upwind from us.

I expect our sensor to jump significantly vs. the other sensor when he starts up the smoker. It’s been two weeks so we’re just waiting for the next “smoker weekend” to see the results.

The particles size distribution is affected by distance. Bigger particulates drop rapidly and are generally fewer. Small particulates travel on long distances and are numerous (increasing the chances that they reach the sensor) but don’t have a lot of mass (so they don’t register well in µg). That could be the culprit explaining the difference between the perceived odor and the PM2.5 / PM10 readings.

Try the “>= 0.3µm / dL” count value to plot your graph.

[…] Smell detects molecules via our olfactory receptors. Sulfur with an approximate molecule diameter of 0.0004 μm is detectable by smell and could certainly pass through an N95 mask. Smoke particles, which are heterogeneous, tend to be larger at approximately 1 μm. However, some smoke particles can be small enough to pass through a mask, and odoriferous gases, such as hydrogen sulfide, may certainly do so. Thus, it is possible to detect certain molecules and particles by smell. […]

I Smell Smoke—The Must Know Details About the N95