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
The KNKA APH4000 is the better air purifier overall, rated 3.4 to 2.9. The KNKA APH4000 leads on value and auto mode. The Medify MA-40 wins on filter cost. The KNKA APH4000 costs $150 less ($99.99 vs $249.99).
Medify MA-40
#7 in Medium roomsFull review
A mid-to-large-room HEPA purifier with cheap filters, for living rooms where noise isn’t a concern.
Amazon $249.99$249.99
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 KNKA APH4000 for value ($0.44 per cfm of smoke CADR vs $1.05 per cfm of smoke CADR) and auto mode (air quality (type not stated) sensor, auto mode vs no air-quality sensor or app).
- Choose the Medify MA-40 for filter cost ($80.34 a year in filters vs $143.96 a year in filters).
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 | KNKA APH4000 | Medify MA-40 |
|---|---|---|
| Overall rating | 3.4/5 | 2.9/5 |
| Value 25% | 100 $0.44 per cfm of smoke CADR | 58 $1.05 per cfm of smoke CADR |
| Filter cost 20% | 23 $143.96 a year in filters | 66 $80.34 a year in filters |
| Quiet 20% | 50 noise at top speed not published (neutral score used) | 0 66 dB at top speed (maker rating) |
| Efficiency 15% | 29 4.3 cfm per watt | 50 efficiency not certified (neutral score used) |
| Auto mode 10% | 70 air quality (type not stated) sensor, auto mode | 0 no air-quality sensor or app |
| Warranty 10% | 25 2-year warranty | 50 warranty not published (neutral score used) |
Specifications
| KNKA APH4000 | Medify MA-40 | |
|---|---|---|
| Performance | ||
| Smoke CADR | 226 cfm | 239 cfm |
| Dust CADR | 226 cfm | 231 cfm |
| Pollen CADR | 244 cfm | 240 cfm |
| PM2.5 CADR | 226 cfm | 235 cfm |
| CADR certified by | AHAM Verifide | AHAM Verifide |
| Room size (AHAM) | 350 sq ft | 370 sq ft |
| Coverage (maker) | 1,695 sq ft | 1,793 sq ft |
| Noise | 22 dB | 46 to 66 dB |
| Efficiency | ||
| Efficiency (IEF) | 4.3 cfm/W | - |
| ENERGY STAR | No | No |
| Energy use | 304 kWh/year | - |
| Filters | ||
| Filter | HEPA-type | H13 HEPA 3-in-1 (pre-filter, carbon, HEPA) |
| Activated carbon | Yes | Yes |
| Replacement | APH4000LX | MA-40 replacement filter |
| Replacement cost | $35.99 every 3 months | $40.17 every 6 months |
| Yearly filter cost | $143.96/year | $80.34/year |
| CARB certified (ozone) | Yes | Yes |
| Controls and build | ||
| Air-quality sensor | air quality (type not stated) | None |
| Auto mode | Yes | No |
| Wi-Fi app | No | No |
| Fan speeds | 4 | 3 |
| Dimensions | 17.09 x 12.36 x 8.15 in | 22 x 10.9 x 9.9 in |
| Weight | 9.7 lb | 15 lb |
| Warranty | 2 years | - |