Dyson Purifier Humidify+Cool HP09 Formaldehyde review: tried and tested

This air-purifying Dyson fan has kept me cool and fixed my hayfever, but... there's a catch

Dyson Purifier Humidify+Cool Formaldehyde
(Image credit: Future)
Ideal Home Verdict

The Dyson Purifier Humidify+Cool Formaldehyde is a smart and sensitive air purifier that's been keeping me cool and hayfever-free this summer. If you've got the space (and the budget), I'd highly recommend it.

Reasons to buy
  • +

    Seamless assembly

  • +

    Very fast reactions

  • +

    Ultra quiet

  • +

    Sanitizes before humidifying

  • +

    Sensitive cooling

  • +

    Easy app compatibility

Reasons to avoid
  • -

    It's a major invesment

  • -

    Takes up a lot of space

  • -

    Not the most portable

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If you send me into the Dyson store with £700 in my pocket, you best believe I'm walking straight past the fans and picking up the coveted Airwrap. That was, until hayfever completely took me out for the last week. 

Even if you're lucky enough to not suffer from hayfever, you may still have heard of the 'pollen bomb' that's been keeping many of us runny-nosed and housebound recently. The Met Office has warned that the high pollen count isn't going anywhere any time soon, and last Sunday, the NHS recieved a call about hayfever every three seconds. 

Admittedly, you probably don't need to invest in the Dyson Purifier Humidify+Cool Formaldehyde to get some much-needed relief this summer, but if you're considering the purchase with hayfever in mind, my review can give you the low-down on just how effective this fan is. 

Launched in March, the Dyson Purifier Humidify+Cool Formaldehyde is Dyson's first purifying humidifying fan. As the name suggests, it also combats formaldehyde, which is one of the most common indoor pollutants in British homes. The chemical is more prevalent in homes with a lot of new furniture, flooring, or upholstery, which can also be an irritant to people who are sensitive to dust, pollen, and other VOCs. 

This fan is hefty, so you won't catch me moving it between rooms this summer. It's also the sort of thing that won't store easily, so expect to use it near-constantly to maintain and track the pollution levels in your home. With that being said though, three months of testing has taught me that this is possibly one of the best air purifier money can buy, and it also works well in the place of one of the best fans for keeping homes cool in the summer. 

Dyson Purifier Humidify+Cool Formaldehyde review: the specs

  • Functions: Purifier, fan and humidifier
  • Power: 45W
  • Cord length: 2 metres
  • Speed settings: 10
  • Oscillation: 90˚ left-right
  • Other functions: no
  • Dimensions: H92.3 x W31.2  x D28cm
  • Weight: 8.2 kg
  • HEPA filter: HEPA H13

Dyson Purifier Humidify+Cool Formaldehydeproduct badge

(Image credit: Dyson)

The Dyson Purifier Humidify+Cool Formaldehyde is an upgraded, Dyson-exclusive version of the Dyson Purifier Humidify+Cool Autoreact. The difference is its ability to pick up formaldehyde in the air and destroy it using a catalytic filter.

Predominantly entering our homes through new products such as flat-pack furniture, upholstery, and flooring, formaldehyde can be particularly damaging for those with breathing problems such as asthma. It's a big one for those who, like me, are in the midst of a home renovation. It's been months since I laid my new carpets and my bedroom still has that chemical, 'new carpet' smell, which is possibly an indication of the VOC's still being given off by the new material. 

How we tested the Dyson Purifier Humidify+Cool Formaldehyde

Millie Fender
Millie Fender

Millie is our Head of Reviews, where she heads up all of our product testing. Formerly our Appliances Editor, she's reviewed just about every kitchen appliance in the business and loves nothing more than getting her hands on a new gadget.

Millie has recently moved into a maisonette in North London, and from fitting new carpets to building flat-pack furniture, she's created plenty of VOCs and dust to really push the Dyson Purifier Humidify+Cool Formaldehyde to its limits. Millie tested the air purifier for a number of months before writing her review, and is looking forward to seeing how it copes with a hot London summer! 

Dyson Purifier Humidify+Cool Formaldehyde review: Unboxing and assembly

Dyson Purifier Humidify+Cool Formaldehyde

(Image credit: Future / Millie Fender)

The good news is, there's absolutely minimal assembly needed with the Dyson Purifier Humidify+Cool Formaldehyde. It arrived in a pretty hefty box, and there was next-to-no plastic packaging to be found. This applies across the board with every Dyson product I've tested, which means I feel a lot less guilty when disposing of packaging.

To set the fan up you need to fill the water tank and slot it into place at the lower front of the machine. As the water goes up through the tank it passes through a λ275nm UV light that ensures it's hygienically dispersed around your room. The tank has a gallon capacity, which means it will last up to 36 hours of continuous use.

Dyson Purifier Humidify+Cool Formaldehyde

(Image credit: Future / Millie Fender)

You also can simply pull the front and rear panels away to switch your filter, and there's a routine reminder to do this on the Dyson App. According to Dyson's site, the filter is designed to only need replacing once every year. The replacements cost £65, so it's not something I'd want to replace regularly.

Instructions were built onto the key parts of the Dyson Purifier Humidify+Cool Formaldehyde, which is a nice tip for ongoing use. The water tank also comes with a handle which made it feel a bit more portable when moving it between rooms.

Dyson Purifier Humidify+Cool Formaldehyde

(Image credit: Future / Millie Fender)

You also need to set up the app when using this fan, which is a necessary evil with most smart products these days. I'll hold my hands up and say that I'm quite app-averse. I prefer on-board controls. And while the Dyson doesn't have these built in, it does come with a little remote that gives you all the same controls as the app. What you don't get is the insights, which is the thing I found most useful about checking in from my smartphone. 

Once your phone is paired to your fan, you can trace the air quality in your home continuously. You need to be near to the fan to check in though, so it's not something you can control from the office, or even a different room. 

Pairing is really easy, it's done via Bluetooth and once your fan is connected there's no need to re-connect it even after unplugging and moving it between rooms. As far as apps go, it's one of the easiest experiences I've had. 

Dyson Purifier Humidify+Cool Formaldehyde

(Image credit: Future / Millie Fender)

Dyson Purifier Humidify+Cool Formaldehyde: Performance

We have a few standardised tests to assess the performance of air purifiers. One of the best things about the Dyson Purifier Humidify+Cool Formaldehyde is that it will tell you when it detects heightened levels of pollution, so you can see in real time how quickly it responds, and how long it takes to return the air quality to average levels. 

The first test was to spray some deodorant in front of the fan while it was in 'Auto' mode. It took a few seconds for the fan to sense the particles, after which it immediately jumped into life. The fan instantly detected a high volume of fine PM2.5 particles, and then began to display the density of these particles on the small sensor at the front of the fan. According to the Dyson app, this technically should've been registered a VOC: 'Odours that may potentiall be harmful. These include cooking, burning fuel, perfume, and cleaning products.'

I was able to watch as this number dropped rapidly, and while it took a couple of minutes for the deodorant smell to completely clear, my sensory experience of the particles in the air aligned with what the fan was telling me. 

Dyson Purifier Humidify+Cool Formaldehyde

(Image credit: Future / Millie Fender)

The second test uses smoke. I sat near my fan, lit a match, and simply let it burn out. It took quite a bit longer for the fan to detect that there were fumes in the air, probably due to the much lower density. It really kicked into high gear once I blew out the final flame, and the match began to release quite a lot of smoke. 

Again, this was detected as a high level of PM2.5. The Dyson app describes this particulate matter as 'microscopic particles smaller than 2.5 microns. These include smoke, industrial emissions, and burning candles.' So, more accurate for the second test than the first. There's no gimmicks here, just a super smart sensor that converts into realtime reports.

Dyson Purifier Humidify+Cool Formaldehyde: Daily use

You're meant to leave this product on all through the day. It's designed to show trends of air quality, humidity and temperature over time, so it's not like a fan that you can simply turn off when it's cooled you down enough. Because of this, I opted for the 'auto' mode most of the time. This automatically adjusted the features to jump into action when needed, without constantly running. 

The fan is basically silent when in Night mode, which means I have no problems sleeping through the night with it running. According to my partner (an early riser) it got a little noisy when he was putting on cologne in the morning, but I slept right through this. The Night mode also dims the display for those who are sensitive to light.

Dyson air purifier tracking

Suffice to say, when I burned some flatbreads on Monday night, the Dyson Purifier Humidify+Cool Formaldehyde seriously freaked out. 

(Image credit: Future)

I tested the Dyson Purifier Humidify+Cool Formaldehyde as the days were entering summer territory. London summer, no less, which meant that I was dreading the sleepless nights and noisy fans I've become accustomed to. The fan is noisy when it's on high cooling mode. It has up to ten speeds, and as my room got hotter throughout the day it amped up the cooling features to combat this, which meant it didn't feel like I was entering a sauna when it came to bedtime. 

As a hayfever sufferer, I was constantly forgetting to take my medication before leaving the house in the morning, so effective was the fan at purifying the air in my home. Even when I had friends around to stay the night, they both noted that their hayfever hadn't kept them up at night, as it usually does, when the fan was running. 

The fan has two main modes, there's a 'breeze mode' which is designed to alter the airflow to give the feel of a refreshing breeze. There's also a diffused mode, designed for the cooler months. By sending airflow through the back side of the machine, it will humidify without as much direct cooling. 

Dyson Purifier Humidify+Cool Formaldehyde: Verdict

Dyson thought of everything when designing the Dyson Purifier Humidify+Cool Formaldehyde. It's got a super smart and user-friendly app, a display with real time stats, and instantaneous purification for daily irritants. What's more, you can track levels of different compounds to get an insight into the air quality inside your home.

The cooling and humidification also play a big role in why I love this fan so much. Even on the highest mode the airflow doesn't feel aggressive or drying, as a regular fan so often can. And when in Night mode, operation is surprisingly quiet.

From where I'm standing, the only downsides are the size, which is pretty bulky when compared to Dyson's regular fan range, and the price, which is a little eye-watering at £700.

I was reluctant to leave any appliance running 24/7 in my home because of the impact it could have on my energy bills. So far, I've not seen a significant jump, although as we get into the warmer months I'll update this review if that changes. 

Millie Fender
Head of Reviews

Millie Fender is Head of Reviews at Ideal Home. She joined Ideal Home as an Ecommerce Editor in 2021, covering all of the site's small appliance and cookware shopping content. Millie formerly worked at Top Ten Reviews, another Future site, where she produced review and buying guides across a range of home products, from fridges to blenders. As Head of Reviews, her job is to test all the wackiest product launches, whether they're air fryers, bread makers, or juicers, and give you her honest experience.