Dyson PM2.5 999 Always Severe [FIXED]

I have a Dyson Pure Cool purifying fan. For a little while, it had been telling me the air quality, in particular, the PM10 and PM2.5 levels were always severely bad. In fact as bad as it can measure, reading of 999.

Looking at the history in the app it hadn’t dropped at all over the last few days so I knew it wasn’t an accurate reading, there must be an issue with the fan.

The Fix

In my case, some dust or other material had gotten into the sensor port causing a false reading. All I had to do was to carefully clean the sensor port.

• I switched off and unplugged the fan.
• I used a hover with a hand held attachment to suck up any dust and other material from in and around the sensor port
• Powered the fan on and within a few seconds the readings returned to what I would expect.

If you are looking at the LCD screen on the front of the fan the sensor ports can be found around the left side of my model (see the below image).

Don’t jam anything in there at most a soft bristle brush! I just used a handheld hover attachment from the outside that was enough in my case.

What is PM 2.5 / PM 10?

PM stands for Particulate Matter – Particulate matter is a complex mixture of soot, smoke, metals, nitrates, sulphates, dust water and rubber etc. The numbers 2.5 and 10 reported by the Dyson fan releate the diameter of the particles in micrometers.

The above fix did not work for me

If my suggested fix did not work for you then you may have an actual fault with your fan. I would recommend reaching out to Dyson support Contact us | Dyson