Dyson's big-room purifier: separate H13 and K-carbon filters, the widest sensor set and directed airflow, at a premium.
Updated
- 100 m² Recommended room size
- H13 HEPA Main filter
- Particle and gas (VOC or formaldehyde) Air-quality sensor
- None Ioniser
Pros
- Built for large, open-plan rooms; UK listings give up to 100 m²
- Separate HEPA H13 and K-carbon filters plus a permanent catalytic filter
- Reads PM2.5, PM10, VOCs, NO₂, formaldehyde, CO₂, humidity and temperature
- Airflow angle of 0°, 25° or 50°, plus a Breeze mode
- Hidden wheels for moving it across hard floors
Cons
- Heavy at 11.9 kg and 83 cm tall
- No particle CADR published; Dyson tested coverage in its own chamber
- Two filters to replace, with no part numbers or intervals on UK pages we read
- No Dyson noise figure on any UK page we read
- Best for
- Open-plan living spaces and large rooms where one machine has to reach the far side.
- Not for
- Small bedrooms, carpeted rooms where you'd want to wheel it often, or tight budgets.
Our verdict
The Purifier Big+Quiet Formaldehyde (BP04, Prussian Blue/Gold, part 545814-01) is Dyson’s purifier for large and open-plan rooms. A cone amplifier on top projects purified air across the room at an angle of 0° to 50°, or in Breeze mode; Dyson’s footnote says it is a fan, not an air-conditioning unit. Its guide suggests the edge of the room, at least 1.1 m (three and a half feet) from the wall.
It has three filters: a 360° HEPA H13 filter, a K-carbon filter wrapped round the body and a permanent catalytic filter for formaldehyde. Dyson tested filtration at 0.1 microns to EN 1822 and formaldehyde removal to GB/T 18801-2022. It senses PM2.5, PM10, VOCs, NO₂, formaldehyde, CO₂, humidity and temperature, the widest set of any Dyson we list.
The big-room claim is the weak point. UK listings give it up to 100 m², but Dyson’s copy says only large open-plan spaces, tested in its own chamber, with no particle CADR, so our guide to what size air purifier you need can’t size it. No UK page we read gives a noise figure, or part numbers and intervals for its two filters. It is also the dearest Dyson we list.
Dyson Purifier Big+Quiet Formaldehyde (BP04) specs
Cleaning
| Clean air delivery rate (CADR) | not listed |
|---|---|
| Recommended room size | 100 m² |
| Main filter | H13 HEPA |
| Activated carbon (odours, gases) | Yes |
Controls
| Air-quality sensor | Particle and gas (VOC or formaldehyde) |
|---|---|
| Auto mode | Yes |
| App control | Yes |
| Ioniser | None |
Size
| Height | 83 cm |
|---|---|
| Weight | 11.9 kg |
Warranty
| Warranty | 2 years |
|---|
Manufacturer figures, checked 2 Nov 2026. — means not listed.
Where to buy the Dyson Purifier Big+Quiet Formaldehyde (BP04)
- John Lewis£899.99Go to John Lewis (opens in a new tab)
- Marks Electrical£899Go to Marks Electrical (opens in a new tab)
Prices and stock change; the retailer’s page is always the final word.
Dyson Purifier Big+Quiet Formaldehyde (BP04) questions
Where is the best place to put a Dyson Big+Quiet in a room?
At the edge of the room on a level floor, at least three and a half feet (about 1.1 m) from the wall, with the cone amplifier aimed at the far point along the wall, Dyson’s guide says; aiming it diagonally across the room also works. Use the airflow angle to aim it, and keep it on hard floors if you plan to wheel it.
How do I reset the carbon filter on a Dyson Big+Quiet?
Hold the down airflow-direction button on the remote for five seconds. The carbon filter wraps round the body under the outer cover and is held by four clips. The HEPA filter has its own reset: hold the Night mode button until the countdown ends and a tick shows. The screen or MyDyson app tells you when each is due.
Do I ever need to replace the catalytic filter on the Dyson BP04?
No. Dyson’s guide says the selective catalytic oxidisation filter is permanent and doesn’t need replacing in normal use. Only the HEPA and carbon filters are replaced, when the screen or MyDyson app asks. No UK page we could read gives their part numbers or intervals, so confirm them with Dyson using your serial number before ordering.
What is Breeze mode on the Dyson Big+Quiet?
A setting you reach by pressing the airflow-direction button on the remote past the 0° to 50° angles; the direction can also be set in the MyDyson app. Dyson sells the BP04’s airflow as able to cool you, but its footnote says it is a fan, not an air-conditioning unit, so it moves air rather than lowering the room’s temperature.
Can the Dyson Big+Quiet be wheeled across carpet?
Dyson designed its hidden wheels for hard floors, so on carpet you may have to lift it, and it weighs 11.9 kg and stands 83 cm tall. If it will live in a carpeted room, choose its spot once and leave it there: Dyson’s guide suggests the edge of the room, aimed along the wall.