CADR against room size, not the marketing number · review
Xiaomi Smart Air Purifier 4 Compact review
A compact HEPA purifier Xiaomi rates at 230 m³/h particulate CADR and 185 m³/h formaldehyde CADR for rooms up to 27 m². An OLED touchscreen shows live air quality, sleep mode is rated at 18.3 dB, and the app tracks a 6-12 month filter life.
The bottom line On paper this is the most affordable of the four purifiers here, and Xiaomi backs the price with a published CADR and a real-time display rather than a bare speed dial. It suits a smaller room; buyers with a larger space should look at the Levoit or Philips instead.
CADR and filtration, as published by Xiaomi
Xiaomi lists a particulate CADR of 230 m³/h and a formaldehyde CADR of 185 m³/h for the Smart Air Purifier 4 Compact, alongside a True HEPA filter rated to capture 99.97% of particles down to 0.3 micron. The brand pairs those numbers with a manufacturer room-size rating of up to 27 m² — a coverage figure Xiaomi publishes itself rather than one derived from an independent test lab. The filter also carries an activated-carbon layer, and Xiaomi states the unit adds a negative-ion output, though it does not publish a separate on/off switch or output rating for that function.
Noise and running cost
Xiaomi’s own figures put sleep mode at 18.3 dB and the top fan speed at 47.4 dB — a wide spread that matters if the unit runs overnight in a bedroom. Xiaomi does not publish a wattage figure for this specific model in the listing we checked, so power draw is marked “Not published” here rather than estimated.
Control and filter tracking
An OLED touchscreen on the body shows live air-quality readings and a filter-life countdown, which is a step up from the single status light common on cheaper purifiers. The unit also pairs with the Xiaomi Home app and, per the manufacturer, works with Alexa and Google Assistant for voice control. Xiaomi’s guidance is to replace the filter every 6 to 12 months, with the exact interval depending on how the display tracks accumulated use.
Size and build
At 350 x 260 x 260 mm and 2.2 kg, this is the most compact of the four units in this roundup — Xiaomi’s own dimensions make it noticeably smaller than the Levoit Core 300S or the Philips 900 Series, which fits the smaller manufacturer room rating.
What is not published
Xiaomi does not publish an exact power consumption figure, a formal certification (equivalent to Philips’ ECARF mark), or a precise ionizer output value for this listing. Where a spec is not stated by the manufacturer, we mark it “Not published” rather than estimate it from similar models.
Bottom line
This is a budget-tier pick built around a genuinely published CADR and a live display, not just a fan behind a filter. It is sized for a bedroom or small room rather than an open living space — buyers who need to cover 50 m² or more should compare it against the Levoit Core 300S or Philips 900 Series reviewed alongside it.
What we like, and what we don't
Strengths
230 m³/h particulate CADR is a strong number for the price bracket
18.3 dB sleep-mode rating is among the quietest Xiaomi publishes for this line
OLED touchscreen shows live PM2.5 and filter-life countdown instead of a vague indicator light
App and voice control are included, not gated behind a subscription
Compromises
Manufacturer room rating tops out at 27 m², modest next to the 900 Series or Core 300S
Xiaomi does not publish an ionizer on/off spec separate from the stated negative-ion output
Filter cartridges are Xiaomi's own part number, not a generic HEPA size
Specifications
Particulate CADR
230 m³/h (Xiaomi PCADR rating)
Formaldehyde CADR
185 m³/h (Xiaomi FCADR rating)
Manufacturer room rating
up to 27 m²
Filtration
True HEPA, 99.97% at 0.3 micron (Xiaomi spec)
Noise, sleep mode
18.3 dB
Noise, high mode
47.4 dB
Filter life
6-12 months, tracked by the OLED display
Control
OLED touchscreen, Xiaomi Home app, Alexa/Google Assistant
Weight
2.2 kg
Amazon reference
B0B6FHKKHP (identical on DE, FR, IT, ES)
Questions people actually ask
What room size does Xiaomi rate this purifier for?
Xiaomi's own specification lists coverage up to 27 m², based on a particulate CADR of 230 m³/h. That is the manufacturer's figure, not an independent lab measurement.
How loud is it on the lowest setting?
Xiaomi publishes 18.3 dB for sleep mode and 47.4 dB for the highest fan speed, so the gap between quiet and full power is wide.
How often does the filter need replacing?
Xiaomi's guidance is every 6 to 12 months depending on use, and the unit's OLED display tracks estimated remaining filter life rather than relying on a fixed calendar reminder.
Sealed HEPA H13 · bladeless tower · fan + purifier
Dyson's Purifier Cool PC1 combines a bladeless tower fan with a fully sealed HEPA H13 filtration system the brand rates at 99.95% removal down to 0.1 micron, tested to EN 1822. Dyson does not publish a CADR figure or an absolute noise-level rating for this model.
Best for: A household that wants one device to handle both summer cooling and air purification and is willing to pay a premium for Dyson's sealed-filtration design and app ecosystem.
Levoit rates the Core 300S at 195 m³/h CADR with a laser particle sensor that drives an automatic mode and a four-colour air-quality ring. Sleep mode is published at 22 dB, and the filter accepts three optional specialty cartridges for pet odour, mould spores or vehicle exhaust.
Best for: A living room or bedroom where automatic speed adjustment and a quiet sleep mode matter, and where the household wants the option to swap in a specialty filter later.
Philips rates the 900 Series at a 250 m³/h CADR for rooms up to 65 m², with a 3-layer HEPA filter the brand states removes 99.97% of particles down to 0.003 micron and carries ECARF certification. Sleep mode is published at 20.5 dB and the filter is rated for up to a year.
Best for: A larger living room or open-plan space where the 65 m² manufacturer rating and long filter life offset the higher entry price.
