TP09 In AUTO won't stop running - Formaldehyde | Dyson Community

TP09 In AUTO won't stop running - Formaldehyde

  • 23 October 2023
  • 2 replies

We have had our new TP09 for about a week now. We really like it and can tell it’s made a difference in the air quality. One thing we have noticed is that is never stops running in auto mode. Definitely due to the formaldehyde which seems to be down to .045-.060. But can’t get lower on its own. If we open windows it will start to read lower. 

is it possible that our house just has that much (5 year old new build) that it can’t keep up on its own? When we first got the TP09 it was sitting at .275. 


Best answer by DavidTaylor 23 October 2023, 14:23

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Hi @NickM

Whilst it doesn’t mention Formaldehyde as a source or cause, I believe the response on the Formaldehyde Cool Purifier doesn't improve air quality especially VOCs has some bearing when considering Formaldehyde, Off-gassing and Pollutants.

What are the common household pollutants? 

(1) Formaldehyde - Produced from Carpets, Rugs and Hard Flooring. Other (Painting, varnishes and printers).

(2) Formaldehyde omits 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. 

(3) With the machine successful reducing the level, even after some time, it suggests the source decreased the rate - as the spike goes away when the space is ventilated, it could mean that something within the home is producing the reading and that it isn’t an outside source. 

(4) Using trial and error try to locate the source. Try 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. 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. 

A somewhat recycled reply that I give full credit to @Stuart for! 



yes I have the same issue. Multiple rooms tested. Window open closed running on high low and so on. Doesnt matter. The Formaldehyde is always between 0,45-0,60 and the thing is running on auto at fan speed 2 all the time.

The funny thing is even when I turn the purifier off it reads the same levels. They never rise. It doesnt matter if the thing runs or not the formaldehyde levels are always the same. So I think the machine is doing nothing. 

I tested 14 hours of machine time and it recored the same 0,55 HCHO levels even when its not purifying.

I dont know what to do.