Dreo 338 Air Purifier
#1 in Small roomsFull review
A cheap, certified bedroom purifier with auto mode for rooms under about 180 sq ft.
Amazon $59.98$59.98
The Dreo 338 Air Purifier is the better air purifier overall, rated 3.5 to 3.2. The Dreo 338 Air Purifier leads on auto mode, value and efficiency. The GermGuardian AC4825E wins on warranty. The Dreo 338 Air Purifier costs $20.76 less ($59.98 vs $80.74).
GermGuardian AC4825E
#6 in Small roomsFull review
A cheap, slim tower purifier for a small bedroom or office.
Amazon $80.74$80.74
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 Dreo 338 Air Purifier for auto mode (PM2.5 sensor, auto mode vs no air-quality sensor or app), value ($0.52 per cfm of smoke CADR vs $0.82 per cfm of smoke CADR) and efficiency (5.5 cfm per watt vs 3.5 cfm per watt).
- Choose the GermGuardian AC4825E for warranty (3-year warranty vs 1-year warranty).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every small rooms air purifier; a clear win is highlighted. How we rank explains each one.
| Factor weight | Dreo 338 Air Purifier | GermGuardian AC4825E |
|---|---|---|
| Overall rating | 3.5/5 | 3.2/5 |
| Value 25% | 99 $0.52 per cfm of smoke CADR | 79 $0.82 per cfm of smoke CADR |
| Filter cost 20% | 50 filter price or life not published (neutral score used) | 50 filter price or life not published (neutral score used) |
| Quiet 20% | 50 noise at top speed not published (neutral score used) | 50 noise at top speed not published (neutral score used) |
| Efficiency 15% | 44 5.5 cfm per watt | 19 3.5 cfm per watt |
| Auto mode 10% | 70 PM2.5 sensor, auto mode | 0 no air-quality sensor or app |
| Warranty 10% | 0 1-year warranty | 50 3-year warranty |
Independent measurements
Dreo 338 Air Purifier
No independent test published yet.
GermGuardian AC4825E
| Tested by | CADR | Noise | Conditions |
|---|---|---|---|
| HouseFresh | - | 55.6 dB | dB at 3 ft: 40 / 44.8 / 51.6 / 55.6 by speed; took 104 min to clear its test room |
Specifications
| Dreo 338 Air Purifier | GermGuardian AC4825E | |
|---|---|---|
| Performance | ||
| Smoke CADR | 115 cfm | 99 cfm |
| Dust CADR | 121 cfm | 116 cfm |
| Pollen CADR | 131 cfm | 129 cfm |
| PM2.5 CADR | 118 cfm | 111 cfm |
| CADR certified by | AHAM Verifide | AHAM Verifide |
| Room size (AHAM) | 178 sq ft | 153 sq ft |
| Coverage (maker) | 856 sq ft | 743 sq ft |
| Efficiency | ||
| Efficiency (IEF) | 5.5 cfm/W | 3.5 cfm/W |
| ENERGY STAR | Yes | No |
| Energy use | 125 kWh/year | 182 kWh/year |
| Filters | ||
| Filter | 3-in-1 filter with carbon layer (HEPA-grade only in sleep mode per Dreo) | HEPA with carbon pre-filter, optional UV-C bulb |
| Activated carbon | Yes | Yes |
| Replacement | DR-HPA032 | FLT4825 (Filter B) |
| Replacement cost | $22.98 | $19.88 |
| Ionizer | No | - |
| CARB certified (ozone) | Yes | Yes |
| Controls and build | ||
| Air-quality sensor | PM2.5 | None |
| Auto mode | Yes | No |
| Wi-Fi app | No | No |
| Fan speeds | 4 | 3 |
| Dimensions | 14.21 x 9.21 x 9.21 in | 22 x 10.25 x 6.75 in |
| Weight | 5.6 lb | 8.6 lb |
| Warranty | 1 years | 3 years |