Reading Calibration Question - VOCs | Dyson Community

Reading Calibration Question - VOCs

  • 24 October 2022
  • 8 replies


We are monitoring VOC levels in a certain room since painting 3 weeks ago. 

Last night after closing the windows, the VOC readings in the room shot up to 5 and HCHO was 0. I tried to adjust the fan speed on my app and accidentally powered off the machine, but I immediately turned it back on. Since it was turned off though, for the past 8 hours the VOC levels have been 0 and the HCHO levels went up to .020. 

Why is it telling me no VOCs are present now but Formaldehyde is? I am confused and this makes me not trust the machine, which we are using to monitor our future nursery. 

We are using the PH04 model. 


(Edited by moderator – Tag and Title amended)


Best answer by Emma.S 25 October 2022, 00:58

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The VOC reading you were seeing is the result of Off Gassing - 

Accidentally switching the unit off, then on again could have plausibly reverted the sensors into a standby state. It’s not something I’ve ever experienced. To be safe, I’d recommend cleaning the sensors, followed up by resetting the machine. This should reboot the sensors and the onboarding software. 

I believe there are a few posts that instruct on this process. I will link them in a follow up message. 


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Thanks for the links. The machine is only a week old, so I don’t think dirty sensors are the issue. 

I did call support and they told me to turn the machine off and unplug for a minute and turn back on. I did that, and the readings are in the green still with low VOC and around .020 formaldehyde. 

I wouldn’t be so anxious if this weren’t helping us decide if nursery air is safe. 

Userlevel 5
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Hi @Choran 

I was in the exact same position 5 months ago. I was very cautious, completely anxious and overthought everything. It never truly goes, even once they arrive 😊! 

I still notice subtle jumps in the VOC reading every time I clean or sanitise the nursery (I am a clean-a-holic), I always monitor until it returns to green. It’s great how accurate they are. 

I wanted to make sure I always got the most accurate reading, one of the other members @Charliebrown recommended I recalibrate the sensors by performing a factory reset. It worked wonders. Maybe you could try the same? 

Emma :)

@Emma.S Haha thank you, it’s hard wanting to do everything perfectly, even though you know it’s impossible. 

Do you find that you need to factory reset often? Does it get “stuck” on elevated levels for a certain reason? Wondering how to know when to trust the machine saying high VOCs and when to reset it. 

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It is. Our first instinct is to protect. We just do it in every way that we can 😊

No, not really. We replaced the filters back in August, straight after we were concerned about the sensors and accuracy. We reset the filter count in the app, cleaned the sensors and factory reset the machine to be sure. It’s working great. 

We’ll certainly be following the same process when we replace the filters next year.

Emma 😊

@Emma.S great, thank you so much for the help!