GermGuardian AC4825E
AHAM verified
- Really cleans
- 150 sq ft14 m² 14 m²150 sq ft
- Box says
- 743 sq ft69 m² 4.9× overstated
- New filter
- 6–8 months
Blueair · Blue Pure 511i Max
Blueair Blue Pure 511i Max
Really cleansAHAM verified
233 sq ft21 m² 21 m²233 sq ft
At 4.8 air changes an hour with a 2.5 m ceiling
- Box says
- Quickly cleans 237 ft² every 12.5 minutes & 1,138 ft² in 1 hourQuickly cleans 237 ft² every 12.5 minutes & 1,138 ft² in 1 hour (106 m²) 4.9× overstated
- New filter
- Every 9 months
Blueair's smallest Blue Pure: light, AHAM-verified, with an air quality sensor and an app. Cleans a large bedroom or a small living room.
Verdict
Who it's for
Cleans a bigger room than its size suggests, and AHAM has verified it. It has an air quality sensor, auto mode and app control. The filter is a Blueair-only part.
Good
- CADR verified by AHAM
- Small and light
- Air quality sensor and app control
Trade-offs
- Filter is a Blueair-only part
- Box headline is based on one air change an hour
Spec facts
Blueair Blue Pure 511i Max · Blue Pure 511i Max
- Really cleans
- 233 sq ft · 21 m²21 m² · 233 sq ftat 4.8 air changes an hour, 2.5 m ceiling
- Box claim
- Quickly cleans 237 ft² every 12.5 minutes & 1,138 ft² in 1 hourQuickly cleans 237 ft² every 12.5 minutes & 1,138 ft² in 1 hour (106 m²)4.9× overstated
- Maker’s claim: Blueair · checked 1 Nov 2026
- Filter
- Blue Pure 511i Max replacement filterParticle + activated carbon, washable fabric pre-filter. Replace every 9 months
- Maker’s claim: Blueair · checked 1 Nov 2026
Certified: measured in an independent lab for AHAM’s Verifide programme. Maker’s claim: the manufacturer’s own figure, not independently checked. Where figures come from
Running it
Filter and upkeep
- Replacement filter
- Blue Pure 511i Max replacement filter
- Type
- Particle + activated carbon, washable fabric pre-filter
- Replace every
- 9 months
- Power at top speed
- 17 W
A new filter every 9 months means 1.3 filters a year. At top speed it draws 17 W: 0.4 kWh if it ran flat out all day. Slower settings use less.
We have no Amazon link for this filter: the maker's page in the sources sells or lists it.
Source: Maker’s claim, Blueair, checked 1 Nov 2026
The box vs the maths
The box says 1,138 sq ft106 m². It really cleans 233 sq ft21 m².
To clean 1,138 sq ft106 m² it would only change the air in the room 1 time an hour. We size every purifier at 4.8 air changes an hour, the level AHAM's room-size guideline works out to.
The box gives two figures. The smaller one, the area it cleans every 12.5 minutes, is 4.8 air changes an hour and close to our figure. The one we show as the box claim is the bigger: the room it can change the air of once an hour.
260 m³/h smoke CADR ÷ (4.8 × 2.5 m ceiling) = 21.7 m² = 233.2 sq ft21.7 m²
Use the calculator for your exact room and ceiling, or read how we pick.
Drawn to scale: the box says “Quickly cleans 237 ft² every 12.5 minutes & 1,138 ft² in 1 hour”, the purifier really cleans 233 sq ft, 4.9 times less.Drawn to scale: the box says “Quickly cleans 237 ft² every 12.5 minutes & 1,138 ft² in 1 hour”, the purifier really cleans 21 m², 4.9 times less.
Room sizes
Which rooms it fits
It suits 161 sq ft15 m² rooms: there it has 40% more air than the room needs, so it needn't run flat out. At 215 sq ft20 m² it only just keeps up (5% to spare), so it would run near its top speed, usually its loudest (why we don’t list noise). In a 107 sq ft10 m² room it's more than twice the size needed; a smaller model does the job.
Under a 2.7 m ceiling it covers 215 sq ft, under 3 m 194 sq ftUnder a 2.7 m ceiling it covers 20 m², under 3 m 18 m², so with a 3 m ceiling it no longer covers 215 sq ft20 m² (why).
For a 269 sq ft room or bigger it's too small, although the box claims 1,138 sq ft: the For a 25 m² room or bigger it's too small, although the box claims 106 m²: the 269 sq ft25 m² page lists models that cover it.
Room pages it qualifies for
Alternatives
The Blueair Blue Pure 511i Max or one of these?
The certified models closest in size, and what is different about each, from the same kinds of source.
Cleans 150 sq ft, 83 sq ft lessCleans 14 m², 7 m² less. It has no air quality sensor. It needs filters more often (every 6–8 months). 19.1 cm taller and 2 kg heavier.
Levoit Core 300
AHAM verified
- Really cleans
- 217 sq ft20 m² 20 m²217 sq ft
- Box says
- 1,066 sq ft99 m² 4.9× overstated
- New filter
- 6–8 months
Cleans 217 sq ft, 16 sq ft lessCleans 20 m², 1 m² less. It has no air quality sensor. It needs filters more often (every 6–8 months) and draws 56 W at top speed. 1.7 kg heavier.
Levoit Vital 100S-P
AHAM verified
- Really cleans
- 217 sq ft20 m² 20 m²217 sq ft
- Box says
- 1,066 sq ft99 m² 4.9× overstated
- New filter
- 6–12 months
Cleans 217 sq ft, 16 sq ft lessCleans 20 m², 1 m² less. It has a different filter schedule (every 6–12 months) and draws 35 W at top speed. 3.8 cm taller and 2 kg heavier.
Sources
Where these numbers come from
- Certified AHAM Verifide directory: Blueair Blue Pure 511i Max · AHAM Verifide
- Maker’s claim Blueair Blue Pure 511i Max product page and specifications · Blueair
We don't test purifiers ourselves: every figure on this page is copied from these sources and was last checked on 1 Nov 2026. Spotted one that's wrong or out of date? Tell us and we'll fix it and change the date.