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Blueair Classic 405 Review

A very powerful air purifier


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With its powerful fan and excellent filtration, the Blueair Classic 405 can quickly clean a room of allergens and pollutants. It's quite a basic-looking device and is relatively expensive, although both of these can be forgiven with the level of cleaning performance that you get.


  • Excellent cleaning performance
  • Very quiet
  • Simple controls


  • No built-in auto mode
  • Quite expensive

Key Specifications

  • Review Price: £499
  • HEPA filter with SmokeStop
  • 6-month filter life
  • 40-square-metre room size
  • 3 speed settings
  • Auto mode via optional Blueair Aware
  • App control
  • Amazon Alexa integration

If you’re tired of your allergies getting you down, the Blueair Classic 405 could be the product for you. This chunky air purifier is designed for medium-sized rooms, with a SmokeStop filter aimed at cleaning the air of all allergens, including smoke, dust and pollen.

Excellent performance and quick room cleaning make it stand out from the crowd, but the high price and basic looks may make some look elsewhere.

The Blueair Classic 405 is large but simple to use, although the app is a little unreliable.

Most air purifiers are really quite simple devices: they suck air in through a filter and blow out purified air the other side. This basic function often means that they’re not the most attractive of devices, and the Blueair Classic 405 definitely fits into the functional category of design. Looking more like a bit of industrial IT equipment, this air purifier is basically a metal case with a fan at one end and a huge filter at the other. Standing at 590 x 500 x 275mm, the Blueair Classic 405 is pretty big, so you’ll need enough space to sit it comfortably. Tucked away in the corner of the room, this air purifier shouldn’t stick out too much.

This air purifier comes configured with everything in place, so you just need to plug in the power cable and you’re good to go. The filter needs replacing every six months, and is easy to change thanks to the large side door. The SmokeStop filters are a whopping £105 a go, although you can use standard filters (£65) instead. The main difference is that the standard filter isn’t designed to deal with gasses or volatile organic compounds (VOCs), which can be present in everything from harsh cleaning chemicals to the glue in old furniture, and the SmokeStop filters are particularly designed for smokers.

Blueair Classic 405 filter

It’s easy to replace the filter, which will need doing every six months

Related: Best air purifiers

Basic controls sit under a flap at the front of the Blueair Classic 405. You can choose from three fan modes and see the current filter status. If you want more control, you need to install the Blueair Friend app and hook your air purifier up to your Wi-Fi network. This should be easier than it is. At first, the app came up with an error while creating an account and wouldn’t let me log in. I had to switch to a different email address to get it working, which is a shame.

Blueair Classic 405 controls

The Blueair Classic 405 has simple controls on the front panel

Once done, I was soon connected and could control the fan speed, and adjust the blue LED light on the front, even turning it off if it were distracting. There’s a scheduled night mode that you can use, too, which automatically turns the fan speed down to 1 (you can set a different speed) and turns the fan off.

Blueair Classic 405 app

The app gives you more control over the air purifier, including a night mode

There’s an Amazon Alexa skill, although it’s a little fiddly to use. For example, you can’t set a fan speed, you can only say increase or decrease speed. You can toggle the machine on and off, which is handy. Google Assistant support isn’t yet available.

There’s no automatic mode on this machine as it doesn’t have any built-in sensors. If you buy a Blueair Aware (£158), you can link this to your air purifier and then control it automatically. There’s an IFTTT channel, which lets you turn the Blueair Classic 405 on or off (you can pick the fan speed from off, 1, 2 or 3), so you could create your own rules using an alternative sensor, such as the excellent Foobot.

The Blueair Classic 405 is very quiet and cleans the air quickly on maximum speed

Running on fan speed 1, I measured the Blueair Classic 405 at 40.5dB from 1m away. That’s little more than background noise in my office. Upping to speed 2, and the sound is very similar with just a small increase to 42.5dB. I’d have expected a bigger jump. On full speed, the Blueair Classic 405 came in at a much louder 54.9dB: you can really it hear it pushing air around, although it’s nice to note that the case doesn’t rattle and vibrate.

The Blueair Classic 405 has high Clean Air Delivery Rate (CADR) ratings, with test result of 476 (Smoke), 510 (Dust) and 510 (Pollen). These are the highest figures for any air purifier that I’ve tested.

In my own test, I lit a smoke pellet, which burns for 60 seconds and then timed how long it took until the Nest Protect in the same room reported that the air was clean again. It took just 5m 41s, which is impressive and the fastest that I’ve seen from any air purifier that I’ve tested.

Switching to a spray of insect repellent, which is a source of VOCs and particulate matter, the Bluair Classic 405 returned my air quality meter to normal readings in 1min 3secs. Again, the best results that I’ve seen.

Should I buy the Blueair Classic 405?

Coming in at £499, the Blueair Classic 405 is one of the more expensive air purifiers you can buy: in fact, it’s only a touch cheaper than the Dyson Pure Hot+Cool, which is also a cooling fan and a heater in one, and has a better app and onboard sensors.

What the Blueair Classic 405 does well is clean the air, effortlessly sucking allergens out the air and delivering the fastest clean-air time that I’ve seen. If you suffer badly from allergies, then this product will help keep your air clean and fresh. If your allergies aren’t so bad and you need more general help, an alternative on our best air purifiers list may work out better for you.

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