We have never been more aware of the fact that air quality matters. With increased discussion of climate change and a focus on respiratory health following the pandemic, we all want to breathe the cleanest air we can.

Outdoors, we encounter allergies and pollutants every day including fumes from traffic, chemicals released by industrial premises and even pollen from plants and trees that can exacerbate eye and nose irritation and cause hay fever. The NHS says around 20 per cent of people living in the UK now suffer from hay fever and these people are around four times more likely to suffer from other allergic conditions such as asthma.

We might reasonably assume that once we’re behind closed doors, we’re much safer. However, one study found indoor air pollution can be over three times worse than it is outside. Everything from cooking to fresh paint is to blame, though there are some less obvious pollutants, from the cleaning products we use to the expensive scented candle we burn while watching TV. We have even less control over volatile organic compounds (VOCs), which are released by some varnishes and paints and even furniture made from MDF or plywood.

Regular ventilation and cleaning are a great first step but still won’t zap microscopic particles or VOCs, so an air purifier is well worth considering. It traps pollutants in a filter and returns cleaned air back into the room. The filter itself will then need regular cleaning and replacing. The best air purifiers offer multi-stage filtration and will adjust the fan speed automatically when they sense pollutants in the air.

On top of this, the Shark air purifier 4 (£179.99, Sharkclean.co.uk) promises to capture a whopping 99.97 per cent of pollutants at 0.3 microns and monitor the air all day long, reporting its results in real-time. Its carbon filter should also work particularly well against smells but can it really make a difference to levels of pollen and other pollutants without a gold-standard HEPA filter? We plugged it in and took a deep breath to find out.

Read more:

How we tested

We left the air purifier running in our kitchen day and night for several weeks to test whether it’s really worth the price tag. We considered how it looked, how noisy it was and how easy it was to operate. We also rated whether it responded quickly and efficiently to increased levels of pollutants and if there was any noticeable difference in the air around us. We also ran the purifier in different rooms including the bedroom while we slept to rate the difference it made to us there too. Here’s what we thought.

Shark air purifier 4 HE400UK

Buy now £179.99, Sharkclean.co.uk

Rating: 9/10
CADR: Not supplied
Room size: 34m² (approx. 85 m³ where 2.5 metres is used as an average height of a room) based on three air changes per hour
Remote control: Yes
Dimensions: 43.2 x 22.6 x 61.7 cm
Power cable length: 1.8cm

Design

There are far more important considerations when buying an air purifier than making a style statement. However, as this is one appliance that will be out on display all year round and can’t be hidden away behind a cupboard door, it’s handy if it looks presentable too.

This Shark model isn’t the best-looking air purifier we’ve seen but it’s hard to find too much fault with its glossy white exterior. We would have preferred if it was white all over though, as the shiny black plastic top surface shows dust and fingerprints very easily.

The purifier’s slim rectangular shape means it’s no hassle to find somewhere to leave it and it won’t take up too much room. However, it looks so much like a sleek mini radiator, one visitor on a sunny day expressed total confusion as to why we had a heater plugged in.

It’s definitely not as big as some other air purifiers we tested though so we soon forgot it was even in the room. A bigger version of the same machine (£199.99, Sharkclean.co.uk) is also available if you want to use it in a room larger than the specified size of 34m².

We really liked the circle of coloured light on the front and top of the machine, which allows you to clearly see the quality of air from the other side of the room. The digital display is also easy to read with three different settings to toggle between to see the percentage of clean air and whether that is good, fair or poor, the time left to clean in minutes and the particle amount in the air. This can display two particle sizes – PM 2.5 for smoke and bacteria and PM10 which includes dust, mould and pollen.

Our only complaint is it would have been great to have somewhere on the machine to store the remote to prevent us from losing it.

Performance

It’s strangely compelling to use this air purifier. Shark’s “clean sense IQ” tracks air quality all day long and automatically adjusts the machine’s cleaning power and fan speed to respond to pollutants as it senses them.

It was fascinating to see what smells and particles triggered a reaction and hear the fans step up a gear when the percentage of clean air fell. It often upped cleaning when our windows were open and went into overdrive when we fried steak on the other side of the room it was in.

It is fantastic at dealing with smells from cooking too. We thought the extractor fan above our hob did a fairly good job until we positioned this air purifier in the kitchen. The built-in carbon filter was unbeatable at neutralising odours, eliminating the smells of a curry we cooked in no time when it would normally linger until the following morning.

However, we were concerned the purifier didn’t include a HEPA filter, which is normally considered the best option for dealing with particles and pollen. Yet Shark says the machine’s multi-staged filtration process traps dirt, dander and particles, and the real-time display certainly backed this up.

The air felt noticeably cleaner too and a mild hay fever sufferer in our family really believed it helped her sleep more soundly than she usually does in summer.

Be aware that Shark determines the suitable room size for this purifier based on three air changes per hour. While this is perfect for anyone looking to improve the general air quality in their home, anyone with severe allergies should really choose a machine that will clean the air at least five times per hour instead.

For our needs, the constant monitoring of air means this model couldn’t be easier to use. Although it can be operated manually with the touchscreen or the remote control, we found the auto mode ideal. You simply plug it in and leave it alone and the purifier will even switch into energy-efficient standby mode when the air is cleaned. Unlike similar machines, there is no accompanying app to see more information on air quality but we didn’t miss this at all.

Though there are four fans, it’s also not too noisy even on full power. However, there is a quiet mode available so it can be used overnight without disturbing your sleep.

The display screen also shows how long is left until the filter needs replacing, which Shark estimates to be between six and twelve months. Helpfully, no washing or maintenance is needed in between changes, so you really can switch this machine on and forget about it.

But be warned, filters can cost up to £59.99 – although they are currently on sale on Shark’s website (£29.99, Sharkclean.co.uk) – so you’ll need to factor in this ongoing cost to running the air purifier.

The verdict: Shark air purifier 4 HE400UK

We were hugely impressed by the Shark air purifier 4 HE400UK and really felt it made a difference to the air quality in our home. We loved the fact it adjusted automatically when it sensed particles in the air so we didn’t need to think about making changes ourselves and we definitely noticed a difference when it dealt with strong smells in particular.

It’s more than a match for models twice its price and a great investment for any home. But severe allergy sufferers may be better off choosing a model that cleans the air more times per hour for maximum impact.

Back to top

Voucher codes

For the latest discounts on home appliances, try the links below:

Keep your floors dust-free while barely lifting a finger with our pick of the best robot vacuums

Thank you for registering

Shark’s air purifier blitzes pollen, dust and pollutants for all-round cleaner air

Can this appliance help us breathe more easily in our own home?