Big difference between HP04 and HP07/09 Sensors | Dyson Community

Big difference between HP04 and HP07/09 Sensors

  • 9 November 2022
  • 3 replies

Userlevel 4
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The sensors between the older HP04 and newer 07/09 seem very different in terms of sensitivity and what is detected. 

I’ve noticed that the 07/09 is extremely sensitive to VOC and takes a long time to come back down whilst not registering NO2 at all. Where as on the 04 as soon as I open the door NO2 spikes (living near a main road I’d expect it to) but VOC doesn’t spike or remain for long when using perfume etc.. 


See screen shots as an example of NO2, 04 and 07 in the same room. 


Anyone else seeing this? 



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3 replies

Userlevel 5
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Hi @Heyhey88,

I guess there aren’t much difference with other sensors apart from the newly added Solid State Formaldehyde.

There was a hugh difference between TP02s and TP04s, as they previously used an IR sensor and it was upgraded to a laser sensor, but between those two machines would not have much of a difference.

In my personal experience, my machines don’t find any big difference on both particulate and VOC readings between two machines. (I own TP04 and TP09)

I guess maybe resetting your machine might be an option, and if the issue persists, you can call the Helpline for a repair. I guess they would change the whole PCB/Sensor module.

Hope this helps!


Userlevel 4
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I’m not convinced it’s a fault, I’ve seen other feedback online that the VOC sensors are crazy sensitive on 07/09 compared to 04’s. I wouldn’t be surprised if there was a change as the newer machines have obviously improved (fully hepa sealed etc..) Would be interested to see if anyone else has feedback. 




Userlevel 5
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I totally understand, and as I’ve advised I would recommend you to try resetting it first in order to know if there’s an issue with your unit.

As you’ve told, it might not be a faulty product, so an option for check this would be to reset your sensors. 

When you use the unit for a certain period of time, normally sensors need to calibrate. That happens to all sensors such as PM, VOC, CO2, NO2 sensors. Even for professional sensors like TSI or another ones would need a calibration process periodically. 

Dyson purifiers would normally re-calibrate everytime when you unplug and turn the machine again. I suggest you to do this, and if the readings vary a lot, you should definately there’s something wrong with your unit.

There could be some difference on sensitivity, but the AQI readings should not show a significant difference. 

I highly suggest you to reset and test your machines and if the issue persists, you could think of getting the sensor replaced.

Hope you have a great day.