At a glance

The Levoit Core 400S is the big brother of the Core 300S — same excellent filtration, same smart features, but 2x the CADR and 3x the coverage. At a street price around $249, it’s the best smart air purifier for large rooms under $300.

The “400S” means it’s the 400-series smart model. If you loved the Core 300S but needed more power for a living room or open-plan space, this is the upgrade.

A Chinese brand, globally trusted

Levoit (深圳市乐沃科技有限公司) is a Chinese home-appliance company with a 50+ country presence. The Core 400S is their flagship large-room purifier, sold on Amazon in the US, EU, and most major markets. Replacement filters are stocked globally.

Design and build quality

The Core 400S is a tall cylinder, about 21 inches high and 9 inches in diameter. It’s noticeably taller than the Core 300S (14.5 inches), so plan for the floor space. The white matte finish matches the rest of the Core series, and the top-mounted color ring shows air quality at a glance (blue = good, yellow = moderate, red = poor).

The build is solid. The filter drawer slides out from the bottom, and the unit is stable. It’s heavier than the Core 300S, so you’ll want to find a permanent spot rather than moving it between rooms.

Performance in real use

The headline number: 240 CFM dust CADR, which is AHAM-verified. That’s the same CADR as the Coway AP-1512HH and the Blueair Blue Pure 211i Max, at a lower price.

In real use, the Core 400S cleans a standard living room (18×20 ft, ~360 sq ft) to under 10 PM2.5 within 15 minutes on high. In a larger open-plan space (500+ sq ft), it works but takes longer — expect 20–30 minutes on high to get the initial dust load down.

The H13 True HEPA filter captures 99.97% of particles as small as 0.3 microns — pollen, pet dander, dust mite debris, mold spores, and smoke particles. The 240g of activated carbon is a genuine secondary filter that handles light odors, cooking smells, and mild VOCs.

Noise

On the lowest “Sleep” setting, the Core 400S runs at about 24 dB — quieter than a whisper. It’s genuinely bedroom-friendly, even for a unit this size.

On the highest setting it reaches ~55 dB, which is comparable to a running shower. You won’t want it on high in a bedroom, but for a quick air reset in a living room, it’s fine. The auto mode is the sweet spot: it starts low and ramps up only when the PM2.5 sensor detects a change.

Smart features

This is where the “S” earns its keep:

  • AirSight Plus — real-time PM2.5 monitoring with a color-coded ring on top
  • Levoit app — air-quality history, scheduling, remote control, filter-life tracking
  • Alexa and Google Assistant — “Hey Google, turn up the living room purifier” works out of the box
  • Sleep mode — dims the display, locks out high-speed settings, stays quiet
  • Auto mode — adjusts fan speed based on the built-in PM2.5 sensor

The app is clean and responsive. You can set it to ramp up at 6 PM when you get home, or run it continuously on auto and forget about it.

Filters and running costs

The Core 400S uses a single combined filter (pre-filter + HEPA + carbon) that Levoit recommends replacing every 6–12 months. The replacement filter costs about $60–70 on Amazon.

That works out to $60–140 per year in filter costs. It’s more than the Core 300S ($30–60/year), but proportionally less than you’d expect for a unit this size. There’s no washable pre-filter, so dust loads the HEPA faster in dusty homes or pet homes.

Who should buy it

  • Anyone with a living room or open-plan space (400–700 sq ft) who wants smart features
  • Smart-home enthusiasts who want Alexa/Google voice control for a large room
  • People with allergies or pets who need high CADR to keep up with dander
  • Anyone who loved the Core 300S but needs more power

Who should skip it

  • Small bedrooms under 200 sq ft — the Core 300 or 300S is cheaper and does the job
  • People on a tight budget — the Core 300S is $100 less and covers 220 sq ft
  • Those who want a Mi Home ecosystem — the Xiaomi 4 Compact has similar CADR for $219

The bottom line

The Levoit Core 400S is the best smart air purifier for large rooms under $300. It has the same AHAM-verified CADR as the Coway and Blueair, but at a lower price with more smart features. If you have a living room or open-plan space and want app + voice control, this is the one to buy.