Formaldehyde Cool Purifier doesn't improve air quality especially VOCs | Dyson Community

Formaldehyde Cool Purifier doesn't improve air quality especially VOCs

  • 30 July 2023
  • 6 replies

Userlevel 1

I’ve already returned one Formaldehyde Cool Purifier mainly because it gave the same high readings of VOCs every night whether it was on, off or in auto mode.  I ordered a replacement and now it is doing more or less the same thing.  In auto mode it switches itself on presumably to deal with the high VOCs but the level does not drop for hours.  It dropped after the same amount of time even if it wasn’t on but was still plugged in and continuously monitoring.  Does this mean the filters are not working for VOCs or the particular VOCs its detecting? Or does it mean it’s creating a false VOC reading? 

I’m also getting whines, whistling and buzzing depending on what settings its on and there seem to be a lot of posts on here about these things that haven’t been resolved by Dyson yet.



Best answer by Stuart 31 July 2023, 16:34

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6 replies

Hello @Florence 

Thanks for reaching out to us and posting this on the community forum. 

Volatile Organic Compounds (VOC’s) are produced from number of sources in the home, such as cleaning products, perfumes, cooking, burning fuels and scented candles.

Our cloud data shows VOC’s increasing in the home through the night and early morning, particularly in winter with added warming effect of central heating combined with reduced ventilation.

Some of these increased can be caused by emissions from our bodies that the VOC sensor can detect.

To read how this data is presented on the In-App Air quality graphs, click on our ‘Viewing your machine's air quality graphs’ article.


Please take a look at this article our CM posted.

 How Air Quality changes throughout the year


Please  here to complete the troubleshooting steps online, if this does not resolve the issue please reach out to our support team.

To do this, simply click on our Guides and manuals link, navigate to the ‘Contact us’ section of the page and select ‘Start a WhatsApp conversation’. 

If you'd prefer, you're welcome to call the Dyson Helpline to speak with our experts directly. You can find their number in the ‘Contact us’ section of the page. 

Hope this helps


Userlevel 1

Hi Audra

Thank you for your answer but it doesn’t really help.  The point I was making is that the fan is not improving the air quality.  Whether it’s on constantly, off but continuously monitoring or in auto mode the air quality remains at the same poor level for hours.  And it’s the summer and some nights the windows are wide open and there’s no heating on.  I have multiple chemical sensitivity so avoid chemicals and perfumes where possible.  I bought the fan to reduce the chemicals off-gassing from furniture and carpets.  But I don’t think this fan is doing that.

I hope you can advise further.


Userlevel 1

If you have opened your room windows during the purifying process, the VOCs might continuously come from the outside into the inside of your room. Hence, the purifier always sucks contaminated air und measures a respective air quality. Or does the described effect also appears with your room windows closed?

Both, my HP09 and my TP09 are able to clean the air with the room windows being closed so that the respective AQ values return to a green level after some time.

Userlevel 7
Badge +13

Hi @Florence

Thanks for posting this here - hopefully I can provide some helpful information.

As mentioned above, Volatile Organic Compounds otherwise known as VOCs are odours that including cooking, burning fuels, perfumes and cleaning products. 

These VOC omit as a gas, which is detected by our Purifiers and are drawn into the machine passing through the filtration system to remove it from the environment. This gas decays at a steady rate as the air in the room is passed through the machine and clean air is expelled - this process can be affected by what is called ‘Off gassing’. This is where a source is producing the gas at a rate higher or the same that equals the machines purification. Read a full explanation on our What is off gassing and what causes it? article. 

As the machine has been successful in reducing the reading, even after some time, it would suggest to me that the source decreased the rate - as the spike came back, it could mean that something within the home is producing the reading. 

As this is the second machine you’ve had, I do not believe there is a fault in production, more so that something locally is causing the reading. The importantly thing is to locate what in the home is producing the gas. This can be done through trial and error. Changing cleaning material, moving the purifier to a different location in the room and/or checking for points when outside air can enter the room are only a few suggestions.

With the above in mind, wiping the sensors on the machine will remove any material on the surface - please following the advice under our Cleaning the sensor. This will help ensure the machine is working optimally. 



@Stuart as detailed as ever, although I’d be keen to hear an outcome from @Florence if this solved the issue or if they had found the cause.

Userlevel 1

Thank you for your replies.

The air quality is fine when the windows are open at other times.

The windows aren’t open every night or are sometimes only slightly open.

The graph shows the same reading of poor air quality for the same amount of time no matter where I place it, no matter how open or closed the windows are AND no matter whether the machine is on, on AUTO or OFF. The air quality improves in the same way after the same amount of time when it is OFF.

For one night only, I had two fans which I placed a few feet apart.  One showed the HCHO levels increasing, the other didn’t.  They both had different readings of VOCs with the second one being lower but still raised.  The second one has now started to look more like the first one did.

As well as the whistles and humming, yesterday it started hissing!