An air purifier in a bedroom runs all night, a few feet from the bed. The quietest air purifier is worth finding, and the box will seem to help: nearly every maker prints a low decibel figure. What the box does not say is that the low figure and the airflow rating describe opposite ends of the machine.
We read the product pages, spec sheets and manuals for fourteen bedroom-sized purifiers from eight brands, and checked them against the EPA, AHAM and ENERGY STAR. This guide covers noise and airflow only. We make no claims about health, and we have left out the health claims on the makers' pages.
Our 6 picks are listed above, with full specifications for each.
The number on the box describes the loudest speed
CADR, the clean air delivery rate, is the standard measure of how much filtered air a purifier delivers. AHAM, which runs the Verifide certification program, says the higher the CADR, the faster the unit filters the air.
The EPA adds the detail that matters here: the rating is typically measured at the air cleaner's highest speed. Its technical summary goes further. Ratings are determined at maximum airflow, and therefore typically at maximum noise. At lower settings, the EPA says, the CADR may not be known, and it could be considerably lower than the advertised figure.
The low decibel figure, meanwhile, describes the slowest speed. So the two headline numbers never describe the same moment.
Three makers publish enough to show the gap:
- IKEA STARKVIND: 29.4 CFM at 24 dB on its lowest speed, and 141 CFM at 51 dB on its highest, with both filters.
- Alen BreatheSmart 35i: 66 CFM at speed 1, rising to 190 CFM on Turbo.
- Rabbit Air MinusA2: 58 to 218 CFM across its range.
What air purifier makers publish about noise
Every speed. Medify alone: 19.8, 37 and 49.3 dBA for the MA-25.
Both ends, labelled. Blueair (19 dB low and 46 high for the 411i+ Max), Alen (lowest and highest speed), IKEA (lowest and highest fan speed) and Rabbit Air.
A range, ends not labelled. Coway (20 to 48 dB(A) for the Airmega 100) and Levoit.
The slowest speed only. Winix, at 23.5dB for the 5510.
Nothing on the product page. Honeywell, for the model we read.
No maker states a measuring distance or names a test standard for its figure. AHAM says a separate standard exists for measuring the sound of room air cleaners, but no maker page we read cites it. The EPA's own summary says noise is seldom reported in a standardized way, which makes devices hard to compare. So treat a gap of a decibel or two between brands as unknown.
Two makers contradict themselves. Blueair's 511 page lists 24 to 49 dB in its spec table and 22 to 44 in its FAQ. Levoit's Core 400S page says 22 dB in one place and 24 in another. We quote both and do not rank either on the lower figure.
For scale, the EPA says a noise rating around 50 decibels is roughly the operating noise of a modern refrigerator. Most top speeds here are close to that.
Size up, and run it on low
This is the practical answer to the trade-off, and the official sources support it.
Start with the room. AHAM's rule of thumb is that the smoke CADR should be at least two-thirds of the room's area. A 10 by 12 foot room is 120 sq ft, so it wants a smoke CADR of at least 80. The EPA's sizing chart, for an 8-foot ceiling, gives 130 CFM for 200 sq ft and 195 for 300.
Then go bigger. The EPA says an air cleaner filters less air at a lower speed. AHAM says a higher CADR simply cleans the air more often and faster. So a unit rated well above your room can run on a quieter setting and still move a useful amount of air. The Blueair 311i Max, rated for 439 sq ft, is our size-up pick.
Compare room sizes on the same basis. AHAM's suggested room sizes assume 4.8 air changes per hour. Makers often headline a lower rate, which gives a bigger number. Medify's headline 413 sq ft is at 2 air changes an hour; at 4.8 it is 172 sq ft. Alen's 700 sq ft for the 35i is also at 2; ENERGY STAR lists that model at 233 sq ft. Levoit prints both, which is the honest way to do it.
Sleep modes, auto modes and lights
A purifier's own lights and settings can matter as much as its fan.
- Sleep modes. Levoit's manual says its sleep mode uses a fan speed lower than low. Coway's manual says the Airmega 100's sleep mode lowers the fan and limits the buttons to half brightness.
- Automatic dimming. The Winix 5510 enters sleep mode when the room goes dark. Rabbit Air and Alen dim their lights in a dark room.
- Auto mode can get loud. Auto modes raise the fan when the sensor detects particles, as Rabbit Air describes. For a steady quiet level at night, choose a sleep mode or a fixed low speed.
- Lights off. Blueair and Levoit have night or display-off settings. IKEA's STARKVIND needs its app and a hub to switch the light off.
Keeping it quiet
Give it space. Levoit asks for 15 inches of clearance on all sides and a flat, stable surface. Coway asks for 20 cm from walls.
Remove the packaging. Levoit and Honeywell both tell owners to take the plastic wrap off a new filter.
Clean the pre-filter. Coway says every 2 to 4 weeks for the Mighty. Rabbit Air says every 3 months or as needed. Levoit says a pre-filter clogged with hair or lint blocks airflow.
Replace the filter when it is due. Levoit's manual lists increased noise as one of the signs.
What it costs to run
Filters are the ongoing cost, and the makers' own prices and intervals vary widely:
- About $25 to $30 a filter: the IKEA STARKVIND ($25, replaced within 6 months) and the Blueair 411i+ Max ($29.99, up to a year).
- About $40 to $55: the Coway Airmega 100 ($39.99 a year), the Blueair 311i Max ($44.99, up to 9 months) and the Alen 35i ($54, 9 to 12 months).
- The Medify MA-25 costs $49.99 a set but lasts 3 to 4 months, which makes it the most expensive to run here on its maker's interval.
Power is small at low speed where makers publish it: about 2 W for the IKEA at its lowest setting, and as little as 0.9 W for the Alen 35i.
What ENERGY STAR does not tell you
We searched the ENERGY STAR room air cleaner specification for noise, sound and decibel, and found none of them. It sets energy efficiency and an ozone limit. An ENERGY STAR listing is still useful here, because it gives each model's CADR and room size on one basis. For the Alen 35i, that listing shows a smoke CADR of 150, where Alen's page says 190 CFM.
Mistakes buyers make
Pairing the quiet figure with the airflow figure. They describe opposite ends of the machine.
Trusting a headline room size. Check the air change rate behind it, and prefer 4.8.
Buying exactly the size of the room. The unit will spend its life on the loud settings.
Leaving it on auto overnight. The fan rises whenever the sensor wakes it.
Reading a bare range as a quiet unit. Coway and Levoit do not say which speed each end of their ranges describes.
New to the units? Read dBA explained. To decide what figure to aim for, see how quiet is quiet enough, room by room. If a product you already own has become noisy, see why your appliance got louder.
How we chose
We read the manufacturer's product page for every purifier, and the spec sheet or manual wherever one is published. We recorded each noise figure in the maker's own words, with the speed each end describes when the maker says. We recorded CADR with its source, preferring AHAM Verifide or ENERGY STAR figures where they exist, and room sizes with the air change rate behind them. We read the EPA's guidance, AHAM's sizing rule and ENERGY STAR's criteria.
We did not measure anything ourselves. We ranked purifiers that label both ends of their noise range, or publish every speed, above those that print a bare range, and we gave credit to makers that publish airflow at low speed. This guide covers noise and airflow only. We make no claims about health, and we have left the makers' health claims out.
