Dyson Purifier Big+Quiet Formaldehyde BP04: problems, parts and running costs

Checked: 2026-10-05

Summary

The recurring complaint is mechanical noise, not filtration: owners in r/dyson report creaking, clicking or grinding on Breeze mode, including on a brand-new unit, with motor bearings that sometimes settle once the fan speed ramps up. Running costs are unusually low, because the HEPA lasts five years, the K-Carbon two, and the Selective Catalytic Oxidation formaldehyde stage is rated for the life of the machine, which works out to roughly $100 a year including shipping and tax. It is a good buy under about $1,000 when formaldehyde or VOC removal is the actual problem, and a poor one at any price for clearing wildfire smoke in a large open plan, because measured throughput of 193 to 200 CFM supports a 302 ft² room, not the 1,000 sq ft Dyson markets.

Common problems and fixes

Creaking, clicking or grinding on Breeze mode — the most repeated owner report. In the r/dyson BP04 thread owners say the units “all make a creaking/clicking/grinding noise on breeze mode,” one brand-new BP04 did the same, and some units add a pop. No source counts how often it happens, so treat it as a repeated signal rather than a known failure rate. Nobody has documented a fix; one owner ties it to room temperature and reports the machine ran quieter after being broken in above 70°F, and another had noise appear at random for a couple of days, suspected a bearing or a flap, and then it stopped on its own. Whether the 2-Year Limited Warranty covers it is undocumented, so assume a noise complaint inside two years needs a support request rather than a known entitlement. [5][6][7]
Rattle on this machine — a separate r/dyson thread is specifically about rattle with the BP04, from an owner who expected a newer, more expensive unit to be free of it. No fix or frequency is reported. [7]
Coverage claim does not match measured output — Dyson markets the machine as engineered for spaces up to 1,000 sq ft and publishes no CADR, while RTINGS measured 329 m³/hr (193 CFM) PM1.0 and computed 302 ft² as the recommended room size at maximum fan speed, and Reviewed measured about 200 CFM for smoke. Not a fault to repair, but sizing the room off the 1,000 sq ft figure leaves the machine undersized; a single unit is a good large bedroom or medium living-and-dining room, and an open 1,000 sq ft plan needs two or three units or a different class of machine. [5][6][8]
No prefilter — one owner in the smoke thread notes it has no prefilter, unlike cheaper units, which matters in a home with pets or heavy wildfire particle loading because there is no washable layer catching hair and lint before the sealed HEPA stage. Workaround is placement and distance: Dyson designs the machine to run from a room corner at least three feet from the wall. [9]
No independent formaldehyde removal rate exists — Reviewed calls this the only unit in its test pool with a catalytic filter dedicated to formaldehyde and rates its chemical filtration the best it has measured, and Dyson states permanent destruction was measured by third-party full-machine testing under GB/T 18801-2022, but no independent lab has published a formaldehyde CADR for this machine. Owners in the same thread argue the stage is not worth much in practice. Nothing here is fixable; ask for the test standard before buying on the formaldehyde feature alone. [5][8][9]
Particle throughput is ordinary for the money — RTINGS’ 193 CFM and Reviewed’s ~200 CFM are roughly what much cheaper machines deliver, and one owner calls it “in every other way it’s an $800 fan.” Also not a defect, but it decides whether two or three cheaper units are the better buy at the same total spend. [5][9]
Warranty length differs by what is covered, and seller matters — the product carries a 2-Year Limited Warranty with a 30-day money-back guarantee, but Dyson’s support page guarantees repair service covering labor and parts, filters excluded, for only 12 months or until service support ends for your machine, whichever comes first. Dyson US sells new units only through a named list of authorized dealers, and Dyson refurbished units are final sale with warranty service only. Buying outside the authorized list puts the warranty and the return window at risk. [5][6][8]

Parts and consumables

H13 glass-fiber HEPA filter (part 972132-01) — $169.99, Dyson spare parts, October 2026. Dyson rates it a five-year life, far longer than the 6-to-12-month norm owners cite for other machines, and the machine shows a filter-change indicator and notifies through the MyDyson app. [5][6][8]
K-Carbon filter (part 972133-02) — $109.99, Dyson spare parts, October 2026. Rated a two-year life. Dyson says this stage captures 3x more NO₂ than the standard carbon filter in the BP03. [5][6][8]
Selective Catalytic Oxidation formaldehyde stage — no replacement part and no consumable cost; Dyson rates it for the life of the machine and says it breaks formaldehyde down into water and CO₂. No catalyst ageing data is published. [6][8]
Replacement remote (part 972178-06) — $29.99, Dyson spare parts, October 2026. The magnetic remote stores on the machine, so losing it is a real replacement rather than a cosmetic one. [5][6]
No replacement fan, motor or electronics parts reported. Dyson publishes step-by-step video guides for replacing both filters on the BP04 support page, and the wheel set is hidden rather than a separately sold part, but no parts catalogue or motor or board spares for the exact model were found, so plan an electronics or motor failure as replacement of the whole unit. [5][6]

Yearly running cost

Filters are the whole bill and there is nothing else. Computed from Dyson’s own part prices in October 2026: $169.99 for the HEPA filter every 5 years plus $109.99 for the K-Carbon filter every 2 years, and the formaldehyde stage never needs replacing. Reviewed amortizes that at roughly $100 a year including shipping and tax and calls it fair against competitors; replacing both filters on schedule comes to about $390 over the first five years. Electricity is not enough data: no source gives an input wattage, a measured draw at Auto-mode duty cycles or a tariff, so there is no yearly power figure to publish. There is no subscription. [5][6][8]

When it is a good buy

Dyson US lists the BP04 at $1,199.99, October 2026; 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 $999.99 at Lowe’s. Read the thresholds against that spread:

At or below $800: strong value for a large bedroom or medium living-and-dining room, because that is roughly the cost of comparable measured throughput elsewhere.
At $979-1,099, the PCMag-observed retailer range: defensible when formaldehyde or VOC removal is the specific requirement.
Around $1,199.99: hard to justify on particle throughput alone, since 193 CFM is what much cheaper machines deliver. [5][6][8]

Alternatives:

Dyson Big+Quiet Formaldehyde BP03 — the base model in Bright Nickel/Prussian Blue, without the K-Carbon filter or the BP04-only CO₂ sensor, at a lower price than the BP04. The better choice when you want the same body and projection without paying the premium for catalytic formaldehyde filtration and the CO₂ sensor. [6][8]
Blueair Blue Pure 311i Max — Reviewed measured about 250 CFM for smoke against this machine’s roughly 200 CFM, in a smaller footprint. The better choice for a room under 300 ft² where particle throughput matters more than formaldehyde capability. [6]
Dreame AirPursue PM10 — an owner comparison puts its consumables at $50 a year for carbon and $100 every 2 years for HEPA, against $100 every 2 years and $170 every 5 years for the Dyson, at the cost of build quality and airflow strength, which the same owner rates lower. The better choice when the budget is the constraint and the formaldehyde stage is not the requirement. [9]
Two or three cheaper high-CADR units at the same total spend — the legitimate answer when the goal is clearing wildfire smoke or purifying a large open plan, because the BP04’s measured 302 ft² maximum-speed room size does not cover one on its own. [5][6]