Dyson Purifier Hot+Cool Formaldehyde review: Quiet, effective and very, very expensive

Dyson’s fans are undeniably expensive but they’re very effective at what they do. So effective, in fact, that it must be tough for its engineers to come up with new ways to update and improve them.

Somehow, though, Dyson does seem to find something new to add every year, and this year’s update to the Hot+Cool purifier range adds to the fan’s ability to detect and filter chemicals from the air.

Thanks to a high-tech new sensor, the fan is now able to detect formaldehyde (HCHO) in the air and can then destroy it using its a new “Selective Catalytic Oxidisation” filter. Formaldehyde is a carcinogen and often found in small amounts in furniture, paint and glue.

Dyson Purifier Hot+Cool Formaldehyde review: What do you get for the money?

Aside from these new Formaldehyde detection and filtering capabilities, however, the new Dyson remains a capable all-rounder, and it can filter all the same stuff as the previous model. It can detect and filter out PM 2.5 and PM 10 particulate matter, volatile organic chemicals (VOC) and nitrogen dioxide, using a pair of HEPA H13 and activated carbon filters in its base.

This time, though, it’s the whole machine that’s rated to the HEPA H13 standard, sealed from inlet to outlet, instead of just the filter. According to Dyson, that means it’s able to filter 99.95% of particles from the air, down to 0.1 microns across, including allergens such as pollen and mould, bacteria and even some virus particles. The latter claim, says Dyson, was tested for by the “independent third-party laboratory” Airmid in Ireland for the capture of Influenza A particles.

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Of course, it also acts as a very effective cooling and heating fan, using Dyson’s patented air-multiplier technology. This keeps things very quiet and hides the fan blades safely away inside the machine, while blowing air through a narrow aperture around the front of the elongated hoop on top of the fan’s filter base.

There are plenty of settings to play with, as you’d expect from a premium fan: three oscillation settings, which allow the Hot+Cool to rotate about its axis by 45, 90 or 180 degrees; a manual tilt mechanism so you can aim the jet of air up or down by a few degrees; and the ability to push air out of the rear of the fan’s hoop for more gentle air circulation.

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Dyson Purifier Hot+Cool Formaldehyde review: How easy is it to use?

Just like other fans in the Dyson range, the Purifier Hot+Cool Formaldehyde is a doddle to use. When you first extract it from the box, you have to unwrap and unseal the filters and install them in the base, but that’s the only faff required.

At this point, you can plug it into the wall and control it using the included remote control, which attaches magnetically to the curved top surface of the fan. A small circular display on the top edge of the fan’s base gives you enough information to set fan speed and direction, oscillation and heat, and it’s very easy to read and see what’s going on.

Alternatively, if you want to get more geeky with the air quality monitoring side of things, set schedules or enable voice control (both Siri and Alexa are supported), you need to download the app and set up a Dyson account. It’s the same app Dyson uses to control its other smart fans and the Dyson 360 Heurist robot vacuum, and it’s very simple to use.

The main screen lets you control the device directly from your smartphone with a series of remote control shortcut buttons, while a swipe up reveals more detailed historical information. Here you can see your indoor air quality on a series of graphs, and a tap of the cog icon in the top right corner lets you turn the fan on and off to a schedule, set up voice control and shop for new filters, as and when needed.

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Dyson Purifier Hot+Cool Formaldehyde review: How effective is it?

For the purposes of this review, I compared the Pure Hot+Cool Formaldehyde with the previous Hot+Cool and the Humidify+Cool fans. The Dyson Humidify+Cool remains the most effective Dyson cooling fan, generating air speeds of up to 3m/sec at a distance of 1m from the front vents.

However, the new Purifier Hot+Cool Formaldehyde is a genuine improvement over the previous Hot+Cool, reaching a peak of 2.6m/sec compared with 2.1m/sec. Not only that, but the new fan is quieter than the old model at its maximum setting, measuring 55-56dBA.

It’s a really effective heater, too, filling small to medium rooms with warm, cosy air in no time at all and capable of heating spaces to a temperature of 27ํ℃. For a quick hit of heat it’s far more effective than your average compact space heater.

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Alas, I had no safe way of releasing and testing the formaldehyde function, beyond noting that, fortunately, the indicated levels were safe in my bedroom and that the fan, according to its own gauges, reduced those levels a touch while it was running.

I did, however, run our usual test on the particulate filtering functions. In a small room, with the fan running at full speed, I sprayed a short burst of anti-perspirant into the air and monitored how long it took the fan to reduce the level of fine particulate matter in the air (PM2.5) to the safe threshold of  25μ/m3.

After the particulate levels reached a rather worrying 124ug/m3 – which, apart from anything, else proves you should never overdo the deodorant without proper ventilation – the Pure Hot+Cool Formaldehyde was able to cut particulates down to below 25μ/m3 in a speedy ten minutes. That’s pretty impressive given the previous model took nine minutes to cut it from a lower peak of 62μ/m3 to 25μ/m3. Clearly, the whole-machine HEPA 13 rating has had a major impact on filtration efficiency.

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Dyson Purifier Hot+Cool Formaldehyde review: Should you buy one?

The Dyson Hot+Cool Formaldehyde is a marked improvement over its predecessor. Not only is it now able to detect and destroy formaldehyde, it’s a more efficient air purifier full stop. It’s also quieter, more powerful and a fantastic space heater, too. If you want a compact, one-box solution to all your cooling, heating and air purifying needs, then the Dyson Purifier Hot+Cool Formaldehyde quite literally stands alone.

However, it’s very expensive and the big question is whether the price justifies these improvements. For £600 you could buy a fan, an air purifier and a space heater, with money left over for a portable air-conditioning unit to boot. If you really do need one device to do it all, then the Dyson will deliver, but you’d better be prepared to dig deep into your wallet.