Last updated: 13 August 2026 · Originally published March 2026 · By James Wright
Evidence checked: 30 July 2026. Product availability, filter prices and manufacturer coverage claims can change.
Research boundary: Smart Home UK did not independently measure CADR, filtration, noise or health outcomes. This guide normalizes current published evidence and exposes missing test bases.
Short answer: compare exact current models using pollutant-specific CADR, room volume, desired air changes per hour, replacement filters and app requirements. Do not treat fan airflow as CADR or an unqualified square-metre claim as a standardized room test.
Correct CADR-to-room calculation
ACH = CADR in m³/h ÷ room volume in m³. Do not multiply by 60 when CADR is already per hour. Source: Consumer room air cleaners: calculating air changes per hour. The previous guide multiplied by 60 even though its CADR values were already in cubic metres per hour; that overstated the result and has been removed.
Current exact-model comparison
| Exact model / UK variant | Published evidence | Smart Home UK normalization | Evidence limits and buying implications | Primary sources |
|---|---|---|---|---|
| Levoit Core 400S Smart Air Purifier, UK listing | CADR 400 m³/h; 166 m² at one ACH and 83 m² at two ACH. Three-stage particle/carbon filtration. Core 400S-RF: 12 months, £65.99 when checked. | Calculated implied room volume at two ACH: 400 ÷ 2 = 200 m³. Implied ceiling height from 83 m²: 200 ÷ 83 = 2.41 m. | Limit: The cited UK pages do not name a CADR test protocol/pollutant or substantiate the old guide's exact H13 wording. Buying implication: Treat the current 400 m³/h evidence as the basis for comparison; the older 260 m³/h, 40 m² and 6–8-month/£30–35 figures are not used here. |
Levoit Core 400S Smart Air Purifier; Levoit Core 400S-RF replacement filter |
| Dyson HEPA Purifier Cool TP09 Formaldehyde, White/Gold | Dyson POLAR test volume: 81 m³. HEPA H13, activated carbon and catalytic formaldehyde filter. HEPA/carbon replacement: one year, £75 when checked. | No particulate CADR is published on the cited UK page. Dyson's 290 litres/second projected fan airflow is deliberately not converted to CADR. | Limit: The model was out of stock at Dyson UK when checked; airflow and CADR are different measurements. Buying implication: Consider it only if current UK availability is confirmed; this guide does not convert 290 litres/second fan airflow into CADR or rely on the older 36 m² figure. |
Dyson HEPA Purifier Cool TP09 Formaldehyde; Dyson TP09 replacement parts |
| Blueair Blue Max 3250i | Smoke, dust and pollen CADR: 239 m³/h each. Published timed claims: 20 m² in 12.5 minutes or 48 m² in 30 minutes. Official filter price: £35 when checked. | CADR is recorded pollutant by pollutant rather than replaced with the old unsupported 280 m³/h aggregate. | Limit: The product page conflicts internally: technical data says six months while the FAQ says up to one year using RealTrack. Buying implication: Budget for a 6–12-month filter interval until the manufacturer resolves its conflicting guidance; actual replacement timing depends on use and conditions. |
Blueair Blue Max 3250i |
| Philips PureProtect 3200 Series AC3220/10 | Particle CADR 520 m³/h under a stated GB/T basis; claimed coverage up to 135 m². Three-layer pre-filter, NanoProtect HEPA and activated carbon. FY3200 replacement life: up to one year. | Treated as a newly assessed current UK model, not a silent specification transfer from AC2958/53. | Limit: The current UK page does not publish an ACH or ceiling-height basis for 135 m². Historical AC2958 official sheets conflict. Buying implication: Compare AC3220/10 only on its own current evidence; historical AC2958 specifications are not applied to it. |
Philips PureProtect 3200 AC3220/10 |
| WINIX T500 WIFI; AT5U207-NWE | CADR 250 m³/h and claimed coverage up to 50 m². Pre-filter, carbon, 99.97%-rated particle filter and PlasmaWave. Filter O replacement interval: 12 months. | Selected as the current UK-delivered replacement candidate; the US-market 120 V/60 Hz C545 is excluded. | Limit: The 50 m² claim has no published ACH/ceiling-height basis. Official delivery is limited to mainland United Kingdom and excludes Northern Ireland. Buying implication: Use the UK-delivered T500 evidence; the US-market 120 V/60 Hz C545 is not a UK substitute, and the room-basis and regional-delivery limits remain material. |
WINIX T500 WIFI |
How this comparison was built
Smart Home UK compared exact current variants against 7 linked official manufacturer, certification or UK government records checked on 30 July 2026. We normalized unlike terminology into a shared decision table and left conflicts visible. This is original desk analysis of published evidence, not a hands-on product test. We did not infer an unreported radio, measurement, warranty, grant status, room basis or retailer route.
What changed and why
- Levoit Core 400S: corrected to 400 m³/h with its published one/two-ACH coverage; the old H13, 260 m³/h and low filter-cost claims were not retained.
- Dyson TP09: retained with an 81 m³ POLAR test volume and no CADR. Projected fan airflow is not relabelled as particulate CADR.
- Blueair Blue Max 3250i: uses 239 m³/h for smoke, dust and pollen. The source’s conflicting six-month versus up-to-one-year filter guidance remains visible.
- Philips AC3220/10: assessed as a current model. It does not inherit the old AC2958 verdict or conflicting historical specifications.
- WINIX T500 WIFI: replaces the US-market 120 V/60 Hz C545. The official mainland United Kingdom delivery restriction, Northern Ireland exclusion and missing room-test basis are explicit limits.
How to size a purifier from evidence
- Measure room length × width × ceiling height to get cubic metres.
- Choose a target air-changes-per-hour rate appropriate to the use and professional advice.
- Multiply room volume by that target ACH to obtain the required CADR in m³/h.
- Check that the manufacturer’s CADR uses a named pollutant/test basis and the exact model.
- Budget the official filter, electricity and app/account requirements. Do not assume maximum-power use represents automatic mode.
For the Levoit published figures, 400 m³/h ÷ 2 ACH = 200 m³ room volume; 200 m³ ÷ 83 m² = an implied 2.41 m ceiling height. That is a reproducible calculation from published inputs, not an independent performance test.
Buying and health limits
An air purifier is not a substitute for source control, ventilation advice, smoke/CO alarms, damp remediation or medical care. Check NHS or qualified professional guidance for asthma, allergy or other health concerns. App control does not improve the underlying filter measurement.
Use official product links in the table while retailer identity is reverified. The two former Amazon buttons both led to one Shark HP072UK listing while appearing under different product sections, so they were removed rather than reassigned to an unverified model.
Estimate electricity and replacement costs with the UK ownership-cost planner, using the exact wattage and filter schedule for the model being considered.
Smart Home UK Team - Research-led UK smart-home editors who compare manufacturer specifications, UK availability, verified owner feedback and authoritative sources. Independent. No sponsored placements.