Dyson Purifier Big+Quiet Formaldehyde

Which model this is

This page covers the BP04, the premium member of Dyson’s Big+Quiet range in Prussian Blue/Gold. Two documented features separate it from the BP03, the base model in Bright Nickel/Prussian Blue: the K-Carbon filter, which Dyson says captures 3x more NO₂ than the BP03’s standard carbon filter, and the CO₂ sensor, which Dyson’s launch page footnotes as included with the BP04 model only. A separate commercial HEPA Big+Quiet Formaldehyde, the BP06, is sold for business use; don’t read its measurements as this machine’s.

Regional machine numbers for the same BP04 body differ: 394809-01 and 410614-01 appear on Dyson US review-page query strings, and 410636-01 shows up inside one retailer’s BP03 path. Metric-market pages list the same body at 830 mm high, 434 mm long and 415 mm wide, 11.9 kg. The Amazon listing for this page is ASIN B0GMKNLJD8; it could not be matched to the BP04 against any non-Amazon source, so every fact here is anchored to the BP04 model designation instead.

Room size and measured airflow

Dyson says the machine is engineered to purify properly in spaces up to 1,000 sq ft, and its metric-market pages say up to 100 m². Dyson publishes no CADR, which Reviewed calls out as the reason this machine is harder to compare than most. RTINGS, the only lab that tested the BP04 specifically, measured 329 m³/hr (193 CFM) for PM1.0 and computed a recommended room size of 28.1 m², or 302 ft², at maximum fan speed. Reviewed measured about 200 CFM for smoke in a sealed lab. Those two lab numbers land in the same place, and both sit well below what a 1,000 sq ft claim implies.

Size the purchase off the 302 ft² figure. This is a good large bedroom or a medium living-and-dining room machine. An open 1,000 sq ft plan needs two or three units, or a different class of machine. Reviewed lists filter-area coverage of 1,200 square feet, which is a different measurement from air delivery and does not settle the question. TechRadar’s formaldehyde sensor can detect molecules 500 times smaller than 0.1 micron, but that is a sensitivity claim about the sensor, not a removal rate for the room.

Formaldehyde and chemical filtration

This is where the machine earns its money. The third stage is Selective Catalytic Oxidation: Dyson says it traps formaldehyde in tunnels and breaks it down into water and CO₂, and that the stage never needs replacing. Dyson also says permanent destruction on the BP03 and BP04 was measured with third-party full-machine testing under GB/T 18801-2022, without publishing a rate.

Reviewed, testing in a sealed lab and at home, calls the chemical filtration the best of any purifier they have tested and describes this as the only unit in their pool with a catalytic filter dedicated to formaldehyde. Owners split on the same point: in an r/AirPurifiers thread, some say the formaldehyde stage is not worth much in practice and that chemists find the reaction less useful than expected. Those posts cite no test. No independent lab has published a formaldehyde CADR for this machine, so ask for the test standard before you buy on the formaldehyde feature alone.

Noise

The picture is genuinely split. Dyson rates the machine 56 dBA maximum and 38 dBA in Quiet Mode, and Reviewed measured 55.6 dBA, which agrees. A verified purchaser on Dyson Canada, who ran it through wildfire smoke, calls it very quiet, and owners in r/dyson describe strong circulation and air you can feel on a second floor. TechRadar’s home-use review also found it quiet at full power, though that piece was written without a sound meter.

Against that, the loudest thread on r/dyson is mechanical. Owners there report that BP04 units “all make a creaking/clicking/grinding noise on breeze mode,” that a brand-new unit produced the same sound, and that motor bearings can grind or squeak until the fan speed ramps up. One owner blames room temperature and says running the machine above 70°F helped. Another had noise appear at random for a couple of days, suspected a bearing or a flap, and then it stopped. A separate r/dyson thread is about rattle with this machine. Nobody has counted how often the creaking happens, so treat it as a repeated signal rather than a known failure rate.

Filters, running costs and value

The consumables are reasonable for a machine this size, and the feature that sets it apart has none. Dyson lists the H13 HEPA filter as part 972132-01 at $169.99 with a five-year life, and the K-Carbon filter as part 972133-02 at $109.99 with a two-year life (Dyson spare parts, 2026-10). The formaldehyde stage is rated for the life of the machine. Reviewed amortizes the two filters at roughly $100 a year including shipping and tax and calls that fair against competitors. Replacing both on schedule comes to about $390 over the first five years, and a replacement remote is $29.99. One owner comparing it with a cheaper machine puts Dyson’s carbon at $100 every 2 years and HEPA at $170 every 5 years, against $50 a year and $100 every 2 years for the cheaper unit.

Warranty length depends on what is covered. The product carries a 2-Year Limited Warranty and a 30-day money-back guarantee, but Dyson’s support page says repair service covering labor and parts, filters excluded, is guaranteed for 12 months or until service support ends for your machine, whichever comes first. Dyson US also sells new units only through a named list of authorized dealers including Best Buy, Costco, Home Depot, Lowe’s, Target, Crate & Barrel, Sam’s Club, HSN and QVC, and authorized refurbished dealers are limited to Nordstrom Rack, Woot and Zulily. Refurbished units from Dyson are final sale with warranty service only. Buy outside that list and you put the warranty and the return window at risk.

Prices vary by source and by date. Dyson US lists the BP04 at $1,199.99 (2026-10), PCMag puts MSRP at $1,099.99 and separately showed $1,099 at Best Buy, TechRadar puts the starting point for the range at $999, and Reviewed linked $1,099.00 at Home Depot on a BP03 path plus $999.99 at Lowe’s. Dyson Canada lists C$1,399.99.

At that spend you are paying for the sealed H13 stage, the sensor suite, 32 ft of projection and the formaldehyde capability, not for particle throughput per dollar. If formaldehyde or VOC removal is your actual problem, this machine has the strongest published lab support in its class. If the goal is clearing wildfire smoke or purifying a large open plan, the measured numbers point elsewhere, and two or three units at the same total spend is a legitimate answer. Check the store panel above before you commit.

Sources

Manufacturer:

• Dyson Purifier Big+Quiet Formaldehyde BP04 product page (Dyson US)
• BP04 spare parts, filter prices and service guarantee (Dyson US)
• BP04 filter and accessory parts (Dyson US)
• Introducing the Dyson Purifier Big+Quiet range, launch claims and BP04-only CO₂ footnote (Dyson US)
• BP04 page with a verified wildfire-smoke owner review (Dyson Canada)
• BP04 page with a verified UK owner review (Dyson UK)
• Placement guidance and BP04 pricing in Australia (Dyson Australia)
• BP03, the base model this one upgrades (Dyson US)
• Authorized dealer list and customer reviews (Dyson US)

Independent reviews:

• RTINGS BP04 test data: PM1.0 CADR and recommended room size
• Reviewed: Dyson Big and Quiet + Formaldehyde air purifier review
• TechRadar: Dyson Purifier Big+Quiet Formaldehyde review
• PCMag’s BP03 review, for where the BP04 sits in the range
• House Fresh’s BP06 review, the separate commercial sibling

Owner reports:

• Breeze-mode creaking and clicking on the BP04 (r/dyson)
• Rattle issues with this machine (r/dyson)
• Thinking about a Dyson air purifier (r/dyson)
• Is the BP04 worth it, and filter interval comparisons (r/AirPurifiers)
• Dyson BP04, CADR discussion (r/AirPurifiers)
• Formaldehyde stage scepticism and smoke use (r/AirPurifiers)
• Cheaper purifier compared with the BP04 (r/AirPurifiers)