How Blueair Purifiers Can Create Dangerous Ozone

Blueair states their air purifiers use HEPASilent technology. They avoid any link to ionizers by claiming that it involves an ‘ion chamber’ that doesn’t emit ions to the room or produce ozone. However, we took apart a Blueair 203 purifier to take a look at this ‘ion chamber’. It turns out, it’s just an ionizer called ‘anion generator’ inside the purifier!

Blueair purifier ionizer dangerous?

It is known that ionizers increase air pollution, creating ozone and particulate. So, do Blueair purifiers produce ozone? And if so, how much do they emit? We’ll find out through experiments.

Blueair purifier ionizer dangerous?

Do Blueair Purifiers Produce Ozone?

Unfortunately, yes, they produce quite a lot of ozone based on our measurements. Blueair emphasizes that its purifiers are CARB-certified to produce ozone less than 50 ppb, exactly the ‘safe’ level. However, when the purifier runs on ‘high’, the ozone level rocketed up and we measured up to 0.181 ppm or 181 ppb very close to the ionizer. It’s also worth noting that the number dropped off rapidly after moving 5-10 cm away from the ionizer.

Are the Ionizers in Blueair Air Purifiers Harmful?

HEPASilent claims to draw charged air pollutants into the purifier so that they can be trapped effectively by the filter, rather than emitting ions into the room. It combines mechanical and electrostatic (not necessary) filtration to remove particles down to 0.1 μm from indoor air without releasing ions, which fundamentally differs from ionizers.

But wait! It doesn’t necessarily mean that 0% get through the filter. In fact, the ion generator is right next to the air outlet. A 3rd party test found that the ionizer function increased the ambient negative ion concentrations from an average of fewer than 2000 ions/cm3 to over 20,000 ions/cm3. It is possible these ions interact with other things in the air to produce dangerous VOCs – something the HEPA filter doesn’t capture.

Although ozone wasn’t tested in this test, tests show ion generators produce a substantial amount of ozone. What’s worse, even relatively low ozone levels can result in increases in particles and formaldehyde.

Read More: 4 Steps to Choosing the Best Air Purifier

Bottom Line: Blueair Purifiers Product Ozone


The HEPASilent Technology is essentially a filter + ionizer, which produces high concentrations of ozone near the ionizer. Considering the ozone production, its harm cannot be ignored. Besides, given the potential for ionization to initiate indoor chemical reactions, further testing should focus on gas-phase organic compounds (e.g., VOCs).

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