Dyson Purifier Hot+Cool Formaldehyde HP09 review

Is Dyson’s latest air purifier its most innovative yet?

Dyson Purifier Hot+Cool Formaldehyde HP09
(Image: © TechRadar)

TechRadar Verdict

The Dyson Purifier Hot+Cool Formaldehyde HP09 is an efficient air purifier and heater/cooler in one. It’s expensive, but this stylish device can remove dust, allergens and formaldehyde from the air in your home, while also regulating temperature, making it a worthwhile buy for those concerned about indoor air pollution.


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    Quickly warms – or cools – a room

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    Built-in LCD panel is useful

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    Control even when you’re away from home


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    Can be loud when heating

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Indoor air pollution, or the dust, dirt, and gases in the air in your home, are a cause for concern for many – and while its effects, such as itchy eyes or a runny nose, may not be noticeable right now, according to the World Health Organization (WHO), 3.8 million people die every year as a result of exposure to indoor air pollution. 

With this in mind, Dyson has unveiled a new version of its air purifier and hot/cold fan in one, which can detect and remove formaldehyde – the most common volatile organic compounds (VOCs) or colorless gasses emitted by the products that we use to clean and decorate homes – that builds up over time, along with other dust and allergens from the air.

The Dyson Purifier Hot+Cool Formaldehyde HP09 looks similar to its predecessors. The freestanding fan sports a tower-like design, with a bladeless oval-shaped fan positioned on a cylindrical base that rotates through 350 degrees to project purified warmed or cooled air around the room. Temperature and speed of airflow can be manually controlled using the remote, or through the Dyson Link smartphone app, while an Auto mode maintains your preferred temperature in the room, adjusting the fan speed as required. 

The Dyson air purifier also detects and traps other dust and allergens from the air through its glass fiber HEPA filter, and provides a detailed breakdown of the air quality and the allergens that have been caught on the unit’s built-in LCD screen. It works in much the same way as its newest vacuum cleaner, the Dyson V15 Detect, which measures the dust it removes from floors in your home, providing a clear picture of just how clean the air in your room is. However, like most Dyson devices, the Dyson Purifier Hot+Cool Formaldehyde HP09 doesn’t come cheap. As such, it would be wise to consider if you really require all of the functions before splashing out, as an individual air purifier, fan heater or cooling solution will be more affordable.

Dyson Purifier Hot+Cool Formaldehyde price and availability

  •  List price $749.99 / £599 / AU$999

The Dyson Purifier Hot+Cool Formaldehyde is priced at $749.99 / £599 / AU$999 and is available to buy in the UK and US right now. It will go on sale in Australia on May 27. Replacement filters for the air purification system are priced at $79 / £65 / AU$99. 

Dyson also offers the Purifier Hot+Cool, which doesn’t have the ability to sense and destroy formaldehyde, but can trap other allergens and dust particles, for $549.99 / £549 / AU$899.

Dyson Purifier Hot+Cool Formaldehyde HP09

(Image credit: TechRadar)


  • Bladeless fan is stylish and safe
  • Oscillates through 350 degrees
  • Integrated sensors analyse air quality

The Dyson Purifier Hot+Cool Formaldehyde HP09 isn’t a compact device, measuring 7.87 x 9.76 x 30.07 inches / 20 x 24.8 x 76.4 cm (d x w x h), although it’s height does allow for it to be placed on the floor or on top of a surface. If you’re thinking about buying an air purifier and a heater/cooling fan, then the fact this is a three-in-one device means you’ll be saving space over buying individual devices.  

As we’ve already mentioned the fan is bladeless, and takes the shape of a loop at the top of the device. This accounts for around half the footprint of the whole device. As well as looking aesthetically pleasing, it’s safer than a fan with traditional spinning blades. 

Offering 10 speed settings, the fan sits on top of a gold cylindrical base that can tilt as well as oscillate through 350 degrees to ensure that air can be projected at almost any angle. The base houses two filters: one for formaldehyde and the HEPA H13 filter that Dyson says captures 99.95% of dust and allergen particles as small as 0.1 microns. The filters are sealed within the machine, so there’s no way for air to bypass them.

The Dyson HP09 detects and traps formaldehyde in its catalytic filter, which then breaks it down into tiny amounts of water and CO2 that are released back into the air. For context, the quantities are so minute that simply being in the room and breathing would release more CO2 into the air than the air purifier. The unit employs an algorithm to ensure that it’s only formaldehyde that’s trapped and destroyed, ignoring other gases emitted into the air from products or processes that don’t affect the air quality. 

The Purifier Hot+Cool Formaldehyde also features a number of integrated sensors that analyse the air quality in the room, with the results displayed on the LCD screen at the base of the unit. The purifier can be controlled via the compact remote, which allows adjustment of the temperature, speed and setting a timer of between 15 minutes and nine hours. The remote comes in the same gold color as the base, and sports a curved design. It’s magnetic, which means it can be neatly stored on top of the fan. Alternatively, settings can be tweaked via the Dyson Link apps, which is available for iOS and Android devices. 

Dyson Purifier Hot+Cool Formaldehyde HP09

(Image credit: TechRadar)


  • Efficient air purification that quickly reduces pollutant levels
  • Efficient when heating and cooling
  • Auto mode maintains temperature of the room

When it comes to purifying the air, we used the HP09 in both our lounge and kitchen. The air quality in the lounge was consistently labelled as Good, with the levels of allergens, gasses and dust remaining stable. For the first minute after we lit a candle and extinguished it, the air quality was heavily impacted, going from Good to Severe. However, within seconds of this change, the air purifier whirred into action and took just under two minutes to return the air quality to the Good status.  

We moved the Dyson Purifier Hot+Cool Formaldehyde HP09 to the kitchen while cooking dinner. After dry-frying sausages and boiling potatoes for 15 minutes without opening a window or using an extractor fan, the air quality had gone from Good to Extremely Poor. According to the air purifier, the PM2.5 level (a rating for microscopic particles smaller than 2.5 microns, such as smoke) and the PM10 level (a rating for microscopic particles smaller than 10 microns, such as dust and allergens) surged from 2 to 152. However, once we’d finished cooking it took less than 20 minutes for the two levels to drop to 32, and a further hour for them to return to normal levels. 

Also impressive was the efficiency with which the Dyson Purifier Hot+Cool Formaldehyde HP09 heated and cooled a room. It took just five minutes for the fan to raise or lower the temperature of a 168 square foot / 16.6 square meter room by one degree. 

When used the unit on Auto mode, which projects heated air into the room to a desired temperature and then stops once it’s reached that specified level, starting again if the temperature dips. We found that in the room the unit was placed, the temperature dipped every 10 to 15 minutes, at which point the fan kicked.

In terms of noise, the fan measured 52db on our decibel meter. While this is equivalent to the gentle hum of a refrigerator, we found the TV wasn’t clearly audible over it. However, when the room was at the desired temperature, the Dyson Purifier Hot+Cool Formaldehyde HP09 registered at just 35db, which didn’t disturb our viewing.

In addition, there’s a Night mode that retains this level of noise and dims the LCD screen, making it good for light sleepers who want the air purifier in their bedroom.

Both filters were easy to fit, making a reassuring snap when they were correctly positioned. Similarly, the filters are just as easy to remove as they are to insert; the LCD screen and the app will notify you when they need changing.  

Dyson Purifier Hot+Cool Formaldehyde HP09

(Image credit: TechRadar)


  • Adjust the temperature, speed and direction of airflow
  • Offers a detailed breakdown of air quality
  • Integration with Amazon Alexa and Siri

The Dyson Link app is easy to use, offering a quick overview of the air quality of the room the unit is in. Swiping up reveals a more detailed breakdown of the different allergens and gasses detected, including a graph that charts their levels over the past week.

Through the app you can also adjust the temperature and speed, activate Night mode and adjust the direction of the airflow. In addition, you can also adjust how far the fan will oscillate and see how much life is left in your filter, while also setting a schedule.

If you have an Amazon smart speaker, such as an Echo or Echo Show, or an iOS device with Siri built in, then you can use the app to enable voice control to turn the air purifier on or off. 

Should I buy the Dyson Purifier Hot+Cool Formaldehyde HP09

Buy it if...

You’re concerned about formaldehyde in the home
If indoor air pollution, particularly formaldehyde, is a concern in your home then this air purifier, which traps and destroys formaldehyde along with other allergens and dust, is a good investment. 

You’re short on space
The Dyson Purifier Hot+Cool Formaldehyde HP09 is an air purifier and heating/cooling fan in one, so if you’re considering purchasing both devices but are tight on space, this could be the answer. 

You value style and function
This air purifier is a good-looking device that’s sure to make a statement in your home. For those who want an air purifier that stands out for the right reasons, this is one for you. 

Don't buy it if...

You’re on a budget
Like most Dyson products, the Dyson Purifier Hot+Cool Formaldehyde HP09 comes at a premium, so if you’re on a tight budget then it isn’t the model for you.

You want a quiet device
On Auto mode, this device proved loud on kicking in when the temperature of the room dropped. As such, if you’re looking for a device that won’t interrupt your leisure time with noise, you’re better looking elsewhere. 

 You want to heat or cool a small space
The Dyson Purifier Hot+Cool Formaldehyde HP09 copes well with large spaces, so if you’re looking for a device that’s suited to a small room, this model is more powerful than you need.  

First reviewed: May 2021

Carrie-Ann Skinner

Carrie-Ann Skinner was formerly Homes Editor at TechRadar, and has more than two decades of experience in both online and print journalism, with 13 years of that spent covering all-things tech. Carrie specializes in smart home devices such as smart plugs and smart lights, as well as large and small appliances including vacuum cleaners, air fryers, stand mixers, and coffee machines. Carrie is now a copy editor at PWC.