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Unusual PM2.5 readings on new indoor sensor

#1

Screenshot 2024-08-13 at 18-49-02 AirGradient
Screenshot 2024-08-13 at 18-49-02 AirGradient3018×1278 162 KB

Hello, I’m really struggling with the PM2.5 readings on the new AirGradient ONE I received yesterday. The PM2.5 readings looked reasonable yesterday, but today they are just bumping along the bottom except for two very brief spikes. The display also shows a reading of just 1 microgram for PM2.5.

It appears to be running the latest v3.1.4 firmware directly from the factory, and I’ve read the instructions carefully. All the other sensors like CO2 appear to be giving reasonable results.

Could someone give me a pointer as to what the trouble might be?

#2

Did anything change in the house at those times? Cooking, opened a bottle of rubbing alcohol or perfume?

Things like that could cause a temporary spike that goes down after a short time.

#3

Thank you for sharing! This is the first time I have seen such a pattern for PM2.5 from AirGradient. Do the PM0.3, PM1, PM10, temperature and humidity readings behave the same? If yes, there is probably something wrong with the monitor (all these metrics are measured by the same module within the AirGradient One).

#4

The PM0.3, PM1 and PM10 readings don’t look correct either, but the temperature and humidity look fine. The CO2, NOX, TVOC also look perfect - it’s just the particulate readings which seem to be consistently low except for very short spikes.

Can you help?

#5

Can you put it outside for a while? You might have some powerful HVAC filters in your house that bring the air quality down to zero except at times of cooking etc.

#6

I understand the PM2.5 readings are consistently at 1 ug/m3 (with the exception of a few temporary peaks). In contrast, humidity and temperature readings change over time as expected. What are the corresponding readings for PM0.3, PM1 and PM10?

If you keep observing the same readings even outdoor: you can try to trigger a response by lighting and extinguishing a candle close to the sensor. Or using a spray such as a deodorant/fragrance. The monitor should respond instantly.

#7

The PM1 and PM10 readings are also consistently almost zero, with occasional short spikes. The PM0.3 readings vary a little bit more, but are still much lower than expected.

I don’t have any kind of air filtering in the house. I’ve tried moving the device to other locations around the house and the results are roughly the same. At this time of year the doors and windows of the house are wide open to the outside.

I tried holding the device near (but not too close!) to a burning lighter with a yellow flame. The CO2 responded immediately by soaring to 3500ppm but the PM2.5 on the device didn’t move from 0.

Thanks everyone for helping me investigate.

#8

Can anyone help me more with this? It does feel like I unfortunately have a faulty device.

#9

I was travelling with limited access to internet, hence my slow reply.

Thank you for sharing the information and doing the test with the lighter! Based on your observations, I also feel like there is an issue with the device.

I suggest two last tests to confirm our suspicion:

  • try using another cable (preferably not longer than 1.5 meter)
  • a burning lighter does not emit as many particles as a candle, so I suggest to repeat that test. I would put the monitor into a room and close the door and all windows. Then I would lit and extinguish a candle 1 meter next to the monitor. The particles should be clearly seen by naked eye when extinguishing the candle (in contrast to the lighter). Alternatively, you can spray some deodorant or fragrance into the room (not directly into the monitor). The PM2.5 readings should increase drastically within a few minutes and stay elevated for a few hours (or until you open a window).

Let us know how these tests work. We are here to help :slightly_smiling_face:

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