Levoit Core 400S
#2 in Medium roomsFull review
A strong all-round pick for a living room or large bedroom, with a real particle sensor and app control at a mid-range price.
Amazon $189.97$189.97
The Levoit Core 400S is the better air purifier overall, rated 3.8 to 3.4. The Levoit Core 400S leads on filter cost, auto mode and efficiency. The KNKA APH4000 wins on value. The KNKA APH4000 costs $89.98 less ($99.99 vs $189.97).
KNKA APH4000
#5 in Medium roomsFull review
A low-priced purifier for medium rooms up to about 350 sq ft. It has a sensor-driven auto mode, but filter costs add up if you follow KNKA’s replacement schedule.
Amazon $99.99$99.99
Prices were last checked October 22, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Levoit Core 400S for filter cost ($49.99 a year in filters vs $143.96 a year in filters), auto mode (PM2.5 laser sensor and Wi-Fi app vs air quality (type not stated) sensor, auto mode) and efficiency (5.8 cfm per watt vs 4.3 cfm per watt).
- Choose the KNKA APH4000 for value ($0.44 per cfm of smoke CADR vs $0.82 per cfm of smoke CADR).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every medium rooms air purifier; a clear win is highlighted. How we rank explains each one.
| Factor weight | Levoit Core 400S | KNKA APH4000 |
|---|---|---|
| Overall rating | 3.8/5 | 3.4/5 |
| Value 25% | 75 $0.82 per cfm of smoke CADR | 100 $0.44 per cfm of smoke CADR |
| Filter cost 20% | 83 $49.99 a year in filters | 23 $143.96 a year in filters |
| Quiet 20% | 53 52 dB at top speed (maker rating) | 50 noise at top speed not published (neutral score used) |
| Efficiency 15% | 48 5.8 cfm per watt | 29 4.3 cfm per watt |
| Auto mode 10% | 100 PM2.5 laser sensor and Wi-Fi app | 70 air quality (type not stated) sensor, auto mode |
| Warranty 10% | 25 2-year warranty | 25 2-year warranty |
Specifications
| Levoit Core 400S | KNKA APH4000 | |
|---|---|---|
| Performance | ||
| Smoke CADR | 231 cfm | 226 cfm |
| Dust CADR | 240 cfm | 226 cfm |
| Pollen CADR | 259 cfm | 244 cfm |
| PM2.5 CADR | 236 cfm | 226 cfm |
| CADR certified by | AHAM Verifide | AHAM Verifide |
| Room size (AHAM) | 358 sq ft | 350 sq ft |
| Coverage (maker) | 1,718 sq ft | 1,695 sq ft |
| Noise | 24 to 52 dB | 22 dB |
| Efficiency | ||
| Efficiency (IEF) | 5.8 cfm/W | 4.3 cfm/W |
| ENERGY STAR | Yes | No |
| Energy use | 237 kWh/year | 304 kWh/year |
| Power at top speed | 38 W | - |
| Filters | ||
| Filter | HEPA | HEPA-type |
| Activated carbon | Yes | Yes |
| Replacement | Core 400S-P 3-stage replacement filter | APH4000LX |
| Replacement cost | $49.99 every 12 months | $35.99 every 3 months |
| Yearly filter cost | $49.99/year | $143.96/year |
| Ionizer | No | - |
| CARB certified (ozone) | Yes | Yes |
| Controls and build | ||
| Air-quality sensor | PM2.5 laser | air quality (type not stated) |
| Auto mode | Yes | Yes |
| Wi-Fi app | Yes | No |
| Fan speeds | 4 | 4 |
| Dimensions | 20.5 x 10.8 x 10.8 in | 17.09 x 12.36 x 8.15 in |
| Weight | 11 lb | 9.7 lb |
| Warranty | 2 years | 2 years |