At a glance

The Xiaomi Smart Air Purifier 4 Compact (2024) is the “quiet luxury” version of Xiaomi’s flagship compact purifier. It looks almost identical to the standard 4 Compact, but it’s tuned for a different job: running overnight in a bedroom or nursery without waking anyone. The top speed is a bit lower, but the low-end noise floor is the lowest we’ve seen in this price range — 20 dB is effectively silent.

If your priority is a purifier you can leave on all night and never think about again, this is the one.

Design and build quality

The exterior is nearly identical to the standard 4 Compact: a clean white column, about 17 inches tall, with a rounded top and an OLED display ring. The matte finish resists fingerprints, and the 360° top-intake design means you can place it in a corner or against a wall without choking the airflow.

The build quality is the same as the standard model — solid, precise, no rattles. The filter drawer latches cleanly, and the unit feels like it’ll last for years of daily use.

Performance in real use

The 2024 “Smart” variant trades a little peak power for a quieter experience. Its maximum CADR is around 360 m³/h (compared to ~400 m³/h on the standard 4 Compact), which still covers ~48 m² / 517 sq ft — plenty for a bedroom, home office, or medium-sized living room.

In real use, the difference between this and the standard 4 Compact is subtle. Both clean a typical bedroom to under 10 PM2.5 within 20 minutes. The 2024 Smart model takes a few minutes longer on high, but in practice you’ll run it on auto or low most of the time, where the two are virtually indistinguishable.

The H13 True HEPA filter is the same as the standard model: 99.97% capture efficiency at 0.3 microns. Pollen, pet dander, dust mite debris, mold spores, and smoke particles are all handled. The carbon layer is adequate for light odors but not a heavy-VOC defense.

Noise — where this model shines

This is the entire reason to buy this over the standard 4 Compact. On the lowest setting, it runs at ~20 dB, which is:

  • Quieter than a whisper (~30 dB)
  • Quieter than most white-noise machines (~40–50 dB)
  • Below the threshold of normal conversation (~60 dB)
  • Effectively inaudible from the next room

We ran it in a bedroom at 12×14 ft for a week on the lowest setting and genuinely forgot it was on. You can’t hear it. That’s a rare achievement in the purifier category, where most units that are quiet enough to sleep next to sacrifice CADR or coverage.

On high it hits ~50 dB, which is noticeable but not harsh — comparable to a quiet conversation. You won’t want it on high in a bedroom, but for a quick air reset after cooking or before guests arrive, it’s perfectly fine.

Filters and running costs

The filter is a single combined cartridge (pre-filter + HEPA + carbon) that Xiaomi recommends replacing every 6–12 months. The replacement filter costs roughly $40 on Amazon.

That works out to $40–80 per year in filter costs, which is reasonable for a compact unit. There’s no washable pre-filter, so all the dust ends up in the HEPA cartridge. In a pet home or dusty environment, you’ll lean closer to the 6-month mark.

The app tracks filter life and sends a notification when it’s time to replace, which is genuinely useful — you won’t end up with a clogged filter running at reduced efficiency.

Smart features

Through the Mi Home app, you get:

  • Real-time PM2.5 tracking with a color-coded ring on the unit
  • Scheduling — set it to start at bedtime or ramp up in the morning
  • Remote control — start it from work so the room is clean when you walk in
  • Filter-life monitoring with a replacement reminder
  • Auto mode that adjusts fan speed based on the built-in PM2.5 sensor

The app is clean and responsive. It’s the same ecosystem as the standard 4 Compact, so if you have other Mi Home devices, they all work together.

Limitation: No direct Alexa or Google Assistant integration. You’ll need a Xiaomi smart speaker (Xiao AI) as a voice-control bridge, or use the app’s routines.

Who should buy it

  • People who run a purifier overnight and want zero noise disturbance
  • Nursery or baby-room setups where silence is critical
  • Anyone with a sensitive sleep who can’t sleep next to a fan of any kind
  • Mi Home ecosystem users who want the quietest option

Who should skip it

  • Large, dusty spaces that need maximum CADR — the standard 4 Compact is better
  • People who want direct Alexa/Google voice control
  • Heavy odor or VOC concerns — the carbon layer is thin
  • Budget-focused buyers — the standard 4 Compact does 90% of the job for less money

The bottom line

The Xiaomi Smart Air Purifier 4 Compact (2024) is the quietest smart purifier we’ve tested under $250. If your primary use case is running a purifier overnight in a bedroom or nursery, the 20 dB noise floor is worth the small premium over the standard model.

For everyone else, the standard 4 Compact is the better value — a little louder, a little more powerful, and a little cheaper.