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Large, powerful and impressive, the Dyson Purifier Big+Quiet Formaldehyde might take up a lot of space, but if you have large rooms (or open plan spaces), and want to keep your air clean, there’s nothing more powerful. With a wide range of air quality sensors, this purifier reacts quickly to pollutants and deals with them efficiently and quickly. It is expensive, but you won’t be disappointed with this purifier’s results.


  • Excellent range of sensors
  • Extremely powerful
  • Very quiet


  • Expensive

Key Features

  • Projects air over 10 metresIs capable of purifying large rooms in your home
  • 360-degree filtration systemCaptures 99.5% of ultrafine particles.


Dyson certainly doesn’t mess about with its product names: it’s clear that the Dyson Purifier Big+Quiet Formaldehyde is a huge air purifier, built to clean the largest of rooms.

With a huge range of sensors, a long-lasting filter and exceptionally quiet performance, if you’ve got space for this purifier, you’ll appreciate it. The high price and large size does mean it’s not one for the masses.

Design and features

  • Filters last up to five years
  • Compatible with MyDyson app
  • Adjustable air flow

Remember the Dyson Pure Cool Me desktop fan? Well, the Dyson Purifier Big+Quiet Formaldehyde looks like a bigger version of this. And, by bigger, I do mean BIGGER – this is a monster of an air purifier.

Measuring 830 x 434 x 415mm and weighing 11.9kg, this air purifier looks like a Star Wars Droid, and needs a fair amount of space to place it. It is mounted on casters, so it’s relatively easy to slide the purifier around, but you’ll still only want to put this in a fairly large room.

Dyson says that the Dyson Purifier Big+Quiet Formaldehyde can project clean air 10m and is suitable for rooms up to 100m², which will cover huge rooms and even entire open-plan layouts.

There are two versions of this product available, with slightly different features. I have the more expensive Dyson Purifier Big+Quiet Formaldehyde, which is finished in Prussian Blue, and has a wider range of features.

There’s also the Dyson HEPA Big+Quiet Formaldehyde, which is cheaper, finished in white, doesn’t work with the MyDyson app, doesn’t have a remote control and doesn’t have an adjustable airflow angle.

Unlike previous Dyson purifiers that I’ve reviewed, such as the Dyson Purifier Hot+Cool Formaldehyde, the Dyson Purifier Big+Quiet Formaldehyde is not specifically a cooling fan as well. It shoots out a burst of air, but it’s not as easy to direct it, nor is the airflow as targeted. Buy this product because you want a purifier, not a multi-function device.

Set up is easy, as the Dyson Purifier Big+Quiet Formaldehyde comes with pre-installed filters, so the device just needs pulling out of the box and plugging in to get started. Filters can last for up to five years, at which point it’s £60 for a new HEPA filter and £60 for an activated carbon filter.

Replacing the filters is easy: pull off the head, press in the clips to slide the external shroud up, and then the HEPA filter can be pulled up and out, and the carbon filter unwrapped from the inside. It’s then a matter of doing the job in reverse to reassemble the purifier.

Dyson Purifier Big+Quiet Formaldehyde inside
Image Credit (Trusted Reviews)

Neatly, the external shroud can be rotated, so the magnetic remote control holder can be moved to the position that you want it in.

The HEPA filter is designed to capture small particles (99.95% of ultrafine particles down to 0.1 microns in size), and the carbon filter is designed to capture gases (benzene, NO2 and more). There’s also a selective catalytic oxidation filter for formaldehyde, which turns the harmful substance into CO2 and oxygen and never needs replacing.

Dyson Purifier Big+Quiet Formaldehyde filters
Image Credit (Trusted Reviews)

As with Dyson’s purifying fans, the remote control can be used for full control over the fan, including manually changing the fan speed, and adjusting the direction of the purifier’s output.

As with the Pure Cool Me, the Dyson Purifier Big+Quiet Formaldehyde takes advantage of the Coanda effect, where air follows the path of a curved surface.

Dyson Purifier Big+Quiet Formaldehyde remote
Image Credit (Trusted Reviews)

By default, the purifier uses Breeze mode, which is designed to simulate a real Spring breeze, but the top and bottom jets can be adjusted, changing the angle of the air. It’s a useful trick to have.

I found that adjusting the airflow meant that I could have the purifier on without being sat in a stream of cold air.

Dyson Purifier Big+Quiet Formaldehyde angle
Image Credit (Trusted Reviews)

While the fan speed can be adjusted manually, it makes more sense to leave the Dyson Purifier Big+Quiet Formaldehyde in Auto mode. Thanks to the wide range of sensors onboard, the purifier can react to lots of pollutants, changing fan speed on demand.

Sensors can detect the amount of particulate matter, which are small particles in the air. There are sensors for PM2.5 (very small particles) and PM10 (small particles). A VOC sensor detects harmful gases, and there are also sensors for NO2 (often caused by cars) and formaldehyde. There are also temperature and humidity sensors for completeness, plus an overall air quality rating that takes into account readings from all sensors.

Dyson Purifier Big+Quiet Formaldehyde screen
Image Credit (Trusted Reviews)

Such a range of sensors means that the Dyson Purifier Big+Quiet Formaldehyde is much more responsive to air quality issues than purifiers that only detect particulate matter. I found that the fan would spin up after I opened the kitchen door, detecting pollutants from outside. Spraying polish to clean a table, the purifier detected increased particulate matter, and spun up its fan.

What Dyson purifiers do make you notice is just how variable air quality is, and how many times you’re exposed to pollutants.

As well as using the remote, the Dyson Purifier Big+Quiet Formaldehyde can also be connected to Wi-Fi and can be controlled using the MyDyson app, home to all of the company’s smart devices, including the Dyson 360 Vis Nav robot vacuum cleaner.

Dyson Purifier Big+Quiet Formaldehyde app
Image Credit (Trusted Reviews)

As well as replicating all of the controls available through the remote, connecting the app gives voice control via Amazon Alexa and the Google Assistant, plus historical records going back seven days showing historical air quality, plus graphs of readings from the individual sensors.


  • Cleans air fast
  • Very quiet

In general day-to-day use, the Dyson Purifier Big+Quiet Formaldehyde is impressive. Its wide-ranging sensors mean that any impurity in the air is detected and dealt with fast, returning the air quality to the green level. Impressively, the purifier only increases fan speed to the point where it needs to clear the current problem, and it’s relatively rare to have it spin up to speed 10.

When the purifier does hit maximum speed, the large fan and clever design mean that it’s still quiet: just 49.8dB from 1m away in my tests. In general use, it’s pretty much impossible to hear this purifier running, and it’s not distracting in the slightest.

To see how quickly it can clear the air, I lit a smoke pellet, which burns for around 60 seconds. I found that the Dyson Purifier Big+Quiet Formaldehyde took just 6m 11s to clear my office of smoke and have the Nest Protect report that the alert was over.

The Dyson Purifier Big+Quiet Formaldehyde did stay on for a total of 15m 50s until it reported the air was completely green: the fan speed was slowly reduced over this period. Overall, this is the fastest and most powerful air purifier that I’ve tested.

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Should you buy it?

You want powerful air cleaning

Extremely powerful and very quiet, this purifier quickly reacts to a range of pollutants and keeps indoor air clean.

You don’t have much space or want a fan too

If you live in a smaller home with smaller rooms, an alternative may suit you more. Likewise, if you want a multi-purpose device, look elsewhere.

Final Thoughts

It takes up a fair amount of room, so the Dyson Purifier Big+Quiet Formaldehyde is really only designed for those with large rooms and plenty of space. It’s also the most expensive air purifier that I’ve reviewed. That said, if you have large rooms (or open plan space) and want a responsive, quiet and powerful air purifier, they don’t come better than this.

If you want something more flexible for a smaller space, then the Dyson Purifier Hot+Cool Formaldehyde may be a better choice, as it’s a heater and fan, as well; otherwise, my guide to the best air purifiers can help.

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How we test

Unlike other sites, we test every air purifier we review thoroughly over an extended period of time. We use industry standard tests to compare features properly. We’ll always tell you what we find. We never, ever, accept money to review a product.

Find out more about how we test in our ethics policy.

Used as our main air purifier for the review period

We test smart purifiers with their apps and we test Amazon Alexa and Google Assistant compatibility.

We time how long it takes each purifier to remove smoke from a closed room.


Is the Dyson Purifier Big+Quiet Formaldehyde a fan as well as a purifier?

It outputs a jet of air, but this isn’t a cooling fan in the traditional sense and is designed for air purification.

How long do the filters on the Dyson Purifier Big+Quiet Formaldehyde last?

Filters can last up to five years depending on usage – the app will tell you when it’s time to replace them.

Full specs

Release Date

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