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Dyson HP09 Pure Hot+Cool Formaldehyde review

Dyson HP09 Pure Hot + Cool Formaldehyde
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Quick verdict: The HP09 Pure Hot+Cool Formaldehyde is Dyson’s best air purifier, best fan and best heater to date, even if the necessity of its main selling point is debatable.


  • Impressive heating, cooling and air purifying properties
  • Easy to control through the app
  • Variety of settings to suit comfort levels

  • Expensive
  • Only comes in one colour option
  • Can be quite noisy at full speed

In this guide

  • Review
Dyson HP09 review

In a time of bushfires, climate change and a global pandemic, the quality of the air we breathe has never been more important.

With this in mind, Dyson has created what is easily its best air purifier yet, in the form of the Dyson HP09 Pure Hot+Cool Formaldehyde.

Priced at $100 more than the regular Dyson Hot+Cool Purifier though, is it worth the extra cost for its additional features? In short: It depends.

Design: Impressive engineering

Dyson HP09 review

Image: Lauren Chaplin/Finder

With its perforated metal base and bladeless design, the Dyson Formaldehyde is almost identical to the previous Hot+Cool HP07 model.

The Formaldehyde also carries over its predecessors' LCD screen which, among other things, displays the quality of the surrounding air in real time.

Strangely, instead of the brand's preferred black/nickel or white/silver colourways, the Formaldehyde is only available in one white/gold colour option (which is actually more of a bronze close up).

While it's certainly not the end of the world, it is an odd colour choice which, unfortunately, does stick out in my otherwise monochrome apartment.

Standing at 76.4cm high, the Formaldehyde is conveniently sized for sticking in a corner or on top of a dresser.

With a 350-degree oscillation angle, it also doesn't matter where in the room you place it – you can still effectively heat or cool the entire space.

There's even a "diffuse mode" which diverts airflow through the back of the machine to purify the air without blowing on you directly, which is a nice addition.

Dyson HP09 review

Image: Lauren Chaplin/Finder

Similar to previous models, the Formaldehyde also comes with a nifty magnetic remote which can be stuck to the top of the machine to prevent you from misplacing it.

If you would rather adjust your unit without getting up though, you can do this through the accompanying Dyson Link app.

How does it work?

Dyson HP09 review

Image: Lauren Chaplin/Finder

To understand how the Hot+Cool Purifier works, we first need to take a look at what formaldehyde actually is.

Essentially, formaldehyde is a colourless gas pollutant which can be released by products such as furniture, paint, varnishes and cleaning products, as well as by natural occurrences like bushfires.

According to the South Australian health department, the formaldehyde levels released by consumer goods, "can be irritating to the eyes, nose, throat and the lungs."

High level exposure can meanwhile have "major toxic effects", and cause "coughing, wheezing, chest pains and bronchitis."

While the effectiveness of any air purifier is difficult to review without scientific equipment, the technology of Dyson's Formaldehyde purifier seems to check out.

One spritz of a cleaning spray immediately sees a huge spike in formaldehyde levels in the room, as depicted by the fancy LED screen on the front of the unit.

After just a few minutes, this level begins to drop back to "normal" as the purifier kicks into gear and removes the formaldehyde from the air. But how exactly does it do that?

Dyson HP09 review

Image: Lauren Chaplin/Finder

In addition to the existing particle, NO2, VOCs, temperature and humidity sensors, the Dyson Formaldehyde also includes a dedicated formaldehyde sensor.

What sets the Dyson model apart from other formaldehyde purifiers though, is the type of sensor it uses.

Rather than the gel-based sensor favoured by other brands, the Dyson Formaldehyde uses an electro-chemical cell, which Dyson claims doesn't dry out and lasts for the entire lifetime of the machine.

Dyson HP09 review

Image: Lauren Chaplin/Finder

This sensor works alongside an algorithm made to precisely monitor formaldehyde levels in the air, while ignoring other gases that are detected by a dedicated VOC sensor.

A Selective Catalytic Oxidisation (SCO) filter then traps and destroys the formaldehyde at a molecular level, breaking it down into small amounts of water and carbon dioxide.

But, do you really need a formaldehyde filter in your home?

Given that the United States Environmental Protection Agency has said that high levels of formaldehyde exposure may cause some types of cancers, it's certainly not a bad idea.

However, as the Agency for Toxic Substances and Disease Registry points out, "most people don't have any health problems from small amounts of formaldehyde in their homes" and small levels can also be offset by simpler measures like opening a window or using an exhaust fan.

In homes that are situated in bushfire-prone areas, or which feature new construction, new manufactured wood products, frequent tobacco smoke or potent cleaning chemicals though, a formaldehyde purification system is definitely a smart investment.


Dyson HP09 review

Image: Lauren Chaplin/Finder

Despite its long and complicated name, the HP09 Pure Hot+Cool Formaldehyde is actually incredibly easy to use.

The remote control offers a range of simple functions which include fan speed, temperature settings, oscillation, automatic mode, diffuse mode and a night time mode which dims the LED screen.

The Dyson Link app is equally user-friendly, as it immediately displays the quality of your air, in addition to the current temperature and humidity level.

When it comes to the filters, Dyson has said that the Formaldhyde's electro-chemical cell will last for the lifetime of the machine, which means you don't need to worry about replacing it.

The purifier also comes with a HEPA filter which can be replaced as needed.

This is a relatively simple process, which involves unlocking the base of the machine, unclipping the old filter and clipping in the replacement.

Dyson has also said that the HP09 Pure Hot+Cool Formaldehyde is 20% quieter than its predecessors.

Certainly on its lowest fan levels, it is barely noticeable. However, at top speed, it can still get quite noisy.

Should you buy the Dyson HP09 Pure Hot+Cool Formaldehyde?

  • Buy it if you're looking for an all-in-one product which not only heats and cools, but can also detect and destroy formaldehyde and other pollutants.
  • Don't buy it if you're looking for an affordable air purifier or are fussy about colour schemes.

As with all of Dyson's products, the main downside of the Dyson HP09 Pure Hot+Cool Formaldehyde is the price tag.

At $999, there's simply no pretending that it's affordable for the average consumer.

When you consider that you are actually getting a heater, cooler and air purifier in one though, the price doesn't seem quite so obscene.

Add to that the ease of use, effective detection and removal of formaldehyde and other pollutants and the fact that it is both child and pet safe, and the purifier is certainly worth shelling out for if you can afford it.

If you don't have reason to believe that there are high levels of formaldehyde in your home though, you can just as easily nab the Dyson Hot+Cool Purifier and save yourself $100.

How we tested

The Dyson HP09 Pure Hot+Cool Formaldehyde was tested over a month-long period. On most days, it was used for several hours per day.

The heating, cooling and purifying capabilities were all used during this time.

Pricing and availability


Base diameter
Cord length

HEPA filter
Oscillation angle
Number of speed settings
Voice Control
Remote control
App control

Images: Lauren Chaplin

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