Just bought HP04 and getting an "Air quality sensor fault" and there's no readings. Turning it on and off doesn't work. Customer support wants me to take it in for repairs. :
Dyson Purifier Big+Quiet Formaldehyde | Dyson
Constantly fluctuating air quality - Is this right? | Dyson Community
Support | Dyson Pure Hot+Cool purifier (HP00) White/Silver
Easy Fix for Dyson Air Quality Sensor Issues
Dyson TP04 reports 999 on PM 2.5 and PM 10 - sensor cleaning - YouTube
Dyson TP04 - cleaning sensor resolves 999 status for PM 2.5 & 10 - YouTube
Dyson TP09 - How to fix the Air Quality sensor issue - YouTube