The PM2.5 sensor on my air purifier shows readings that drift over time
Home Nura guide — category: Air Purifiers
Diagnosis
This symptom isn't trivial, but in most cases you can fix it without calling in a pro. Work through the steps below in order and stop as soon as the problem clears up.
What to do
1. Unplug it and let it cool. 2. Inspect the parts you can reach. 3. Follow the manufacturer's procedure (owner's manual or official website). 4. If the fix means taking the unit apart, stop and contact customer support so you don't put the warranty at risk.
Repair or replace?
If the problem is still there after these checks and the appliance is out of warranty, weigh the repair estimate against the cost of a new model.
If you're replacing it
Air Purifiers: the picks from our buying guide
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Best overall
Levoit Core 400S
HEPA filter, a claimed CADR of 235 CFM (400 m³/h), a laser PM2.5 sensor and sleep mode: versatile enough for a living room by day and a bedroom at night.
Photo: © Levoit
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Best value
Levoit Core 300S
Compact, with a HEPA filter, a claimed CADR of 141 CFM (240 m³/h), auto mode and about 22 dB in sleep mode: the essentials for a bedroom.
Photo: © Levoit
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Quietest for sleeping
Blueair Blue Pure 411i Max
A claimed noise range of 18 to 46 dB, a washable pre-filter, a PM2.5 sensor and an app: ideal for light sleepers.
Photo: © Blueair
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Other common problems in this category
These issues affect the same type of appliance — each one comes with a diagnosis and the steps to take.
Frequently asked questions
Check the manufacturer's warranty first: how long it lasts and what it covers vary by brand and model, so read the terms for yours and keep your proof of purchase. If you bought it new in the EU, a two-year legal guarantee also applies (Directive (EU) 2019/771), covering defects present at delivery, whenever they first show up.
If you're still within the seller's return window, a return or exchange is usually the fastest fix. After that, go through the manufacturer's support team: it handles warranty claims and can often repair the unit even after the warranty has run out. Either way, keep your proof of purchase.
Our public methodology lowers the Nura Score /10 of any model in our Air Purifiers guide whose recurring failures show up in owner reviews. A model that breaks down too often never makes it to the top, whatever the brand.
Generally, yes, if you stick to routine maintenance: cleaning, replacing a gasket, recalibrating. Irreversible changes to the hardware are what can cause problems, so read your warranty terms before you open anything up. Anything the manufacturer's manual walks you through is the safe zone.
Your proof of purchase, the exact model name and a record of the symptom: photos, a short video, the sound it makes and any error code. Note when the problem started and what you've already tried. With all that in hand, support can pin down the problem much faster.