Dyson has some of the best air purifiers, largely because of the quality of its sensors that let the fan speed adjust automatically to always keep your air clear. If you’ve noticed that your fan has started to show the PM2.5 and PM10 levels as severe, with readings of 999, don’t panic: your air is unlikely to be this filthy, but rather the sensor has become clogged.
Here, I’ll show you how to fix the issue quickly and efficiently, so that you can get back to your fan purifying correctly. Although I’m using the Dyson Pure Cool Tower in this example, the steps apply to all other fans, including the Purifier Hot+Cool Formaldehyde and the Pure Cool+Humidify.
Why do the fan and app show such high PM levels?
Particulate matter (PM) are small particles of dust that can cause breathing problems and trigger asthma attacks. Dyson distinguishes between very small (PM2.5) and very large (PM10) particles, giving a reading for each, but they’re detected by the same sensor.
Usually, the sensor operates by measuring particles as they pass over it. If the sensor or its opening port get clogged with dirt, the sensor can malfunction and give you a permanently wrong reading, with the fan’s screen and app warning you about severe levels.
If this level doesn’t drop as the fan runs or you notice in the app’s history that the level has been at Severe for days, then it’s likely that the sensor is blocked. Below is a breakdown detailing how to clean it.
Locate your sensor
All Dyson purifying fans have cut-outs on the case, with the sensors located behind them. Typically, if you look at the front of the fan, and then spin it around, you’ll find the sensors located towards the back of the unit. Depending on the model, these cut-outs can be on the left- or right-hand side of the fan.
The number of holes depends on the sensors inside. With the Pure Cool Tower, for example, there are two cutouts. The Purifier Hot+Cool Formaldehyde has four, as this model has additional sensors for detecting more pollutants.
Clean around the sensor
First, you should unplug your fan, so that it’s completely off. Then, you can start to clean it. I recommend giving the fan a thorough cleaning all over first. I used the dusting brush on a vacuum cleaner to clean around the ports and to tackle the perforated filter enclosure.
It’s worth vacuuming at the front of the fan, around the controls and around the main fan head, too. You can wipe the fan with a damp microfibre cloth, too. Make sure you clean around the sensor ports, too, but don’t stick anything through them to avoid damaging the sensors.
Vacuum out the sensor
Next, you need to vacuum out the sensor, removing any dirt from the inside. To do this, you need a vacuum cleaner with the best attachment to cover the ports. For me, I used the flexible nozzle tool that came with my Vax Blade 4. Pressing this up against a port, I put the vacuum cleaner onto its Turbo setting, making sure I had as good a seal as possible: you may want to get someone to help so that you can press your fingers around the nozzle to seal any air gaps. Repeat for any other sensor ports you have, giving the vacuum cleaner a good 10 seconds or so on each one.
Turn your fan back on
You can now plug your fan back in, and turn it on. It takes a few seconds for the sensors to start taking accurate readings, but your fan should now show air levels are back to normal; at the least, you should not have a Severe reading and, as the fan runs, PM levels should drop.
If you still get a Severe level of PM, then repeat the steps above to really make sure that you’ve got everything out. If you don’t have any luck, then you’ve probably got a bigger issue with your purifier and will need to call Dyson support.
If you need a replacement but don’t fancy picking up another Dyson you can also check out our list of the best air purifiers, which details the top scoring products we’ve tested.