An air purifier in a bedroom has one job that matters more than the rest: run all night, a few feet from your head, without keeping you awake. So the number to look for is not the one on the front of the box. It is the figure for the setting you will actually leave on at night, and most makers do not say which setting their low figure describes.
If the purifier is one of several machines running at night, our page on keeping an apartment quiet puts them side by side.
This guide is the bedroom follow up to our main guide to the quietest air purifiers. That guide explains why the airflow rating and the quiet figure describe opposite ends of the machine. Here we look at the night: which makers publish a figure for their sleep or night mode, how to size a unit so its quietest setting is enough for a typical bedroom, and which lights and auto modes stay calm after dark. We make no health claims, and we have left the makers' health claims out.
Our picks are listed above, with full specifications for each.
What 20 to 30 dB means in a quiet bedroom
The World Health Organization's community noise guidelines recommend less than 30 A-weighted decibels, 30 dB(A), in bedrooms during the night for a sleep of good quality. That figure is for the whole room: the purifier, the street, the fridge down the hall and everything else together.
For scale, the US National Institute on Deafness and Other Communication Disorders puts whispering at 30 dB. The National Park Service describes 20 dBA, the level along some remote trails in the Grand Canyon, as softer than a whisper. So the low figures in this guide, from 19 to 27, describe a machine that is meant to sit right at or under the level of a whisper.
That matters in a bedroom in a way it does not in a kitchen. In a quiet room at night there is very little else making sound, so a purifier running at 25 dB can easily be the loudest thing you hear. The National Park Service explains the scale: every 10 decibels is a doubling of perceived loudness and a ten-fold increase in sound level. It follows that two sources at the same level add up to only about 3 decibels more than one of them, and a source 10 decibels below the rest of the room adds very little. In a room that is already at 30, a 20 dB purifier barely registers. In a room that is nearly silent, the same purifier is what you hear.
Two cautions apply to every figure here. First, no maker states the distance it measured from or the standard it used, so a gap of a decibel or two between brands tells you nothing. Second, units and settings differ: Blueair, Winix and Levoit print dB, Medify and Coway print dBA or dB(A), and Alen prints dB on its spec line and dBA in its comparison table. Each figure also describes a different setting. We quote each one as printed and do not rank one against another.
A purifier's lowest published figure is only useful at night if it describes the night setting. Here is what each maker says:
- Levoit Core 200S-P. The clearest. Levoit's page says Sleep Mode runs "with noise levels as low as 27dB", and the manual says Sleep Mode uses a fan speed lower than speed I.
- Winix 5510. Winix's page says "Nearly silent on slowest speed (23.5dB)". Its manual says Sleep Mode sets the fan to a minimum speed lower than Low, which makes Sleep Mode the slowest speed. So the 23.5dB figure is the one you would hear at night. It is also the only figure Winix publishes.
- Blueair Blue Pure 411i+ Max. Blueair lists 19 dB for its low setting. Its own guide to the Blue Pure Max speeds calls Night mode the lowest fan speed and Speed One the "low fan speed". It does not say which of the two the 19 dB figure describes. Night mode may be the same or quieter, but Blueair does not publish a figure for it.
- Medify MA-25. There is no separate night speed in the manual, so speed 1, at 19.8 dBA, is the night setting. The manual also has a dimmer.
- Alen BreatheSmart 35i. Lowest speed, 23 dB, which is also 66 CFM of airflow.
- Coway Airmega 150. A range of 19.98 ~ 48.3 dB(A), with neither end labelled, and no sleep mode on the product page.
Levoit's 27dB leaves only a few decibels under the WHO's 30, but it is the only figure here tied to the sleep setting in the maker's own words. We would rather have that than a figure at an unnamed speed.
Sizing for a typical bedroom
AHAM's rule of thumb is that the smoke CADR should be at least two-thirds of the room's floor area. For common bedroom sizes, that works out to:
- 10 by 10 feet, 100 sq ft: smoke CADR of at least 67. The EPA's chart gives 65 for 100 sq ft.
- 10 by 12 feet, 120 sq ft: at least 80.
- 12 by 14 feet, 168 sq ft: at least 112.
- 14 by 16 feet, 224 sq ft: at least 149. The EPA's chart gives 130 for 200 sq ft.
Those are minimums, and they assume the unit runs at the speed its CADR was measured at, which the EPA says is typically the highest. At night you will not be running it there. So the practical rule for a bedroom is to choose a unit whose room size, at AHAM's basis of 4.8 air changes an hour, is well above your room. The makers' own figures on that basis:
- Levoit Core 200S-P: 140 sq ft
- Medify MA-25: 172 sq ft
- Coway Airmega 150: 214 sq ft
- Alen BreatheSmart 35i: 233 sq ft (ENERGY STAR listing)
- Blueair Blue Pure 411i+ Max: 259 sq ft
- Winix 5510: 392 sq ft
In a 12 by 14 foot bedroom, the Levoit and the Medify are close to their limit, and they would need their louder speeds to keep up. The Coway, Alen, Blueair and Winix all have room to spare.
How much air a unit moves on its night setting is rarely published. Alen publishes it: 66 CFM at speed 1 against 190 on Turbo, about a third. IKEA's STARKVIND manages 29.4 CFM at its lowest speed against 141 at its highest, about a fifth. That is why we size up for a bedroom. A unit rated for twice your room has twice the margin when it is turned down.
Lights that stay on
A purifier's display can bother a light sleeper as much as its fan. Here is how each one handles the dark:
- Levoit Core 200S-P: the display turns completely off within 6 seconds of choosing Sleep Mode. The night light is separate, has two brightness levels, and is switched off with its own button.
- Blueair 411i+ Max: in Night mode, Blueair says the LEDs are fully dimmed.
- Winix 5510: Sleep Mode switches off the air quality light, and the page says it dims the LEDs.
- Coway Airmega 150: Coway says you can turn off the light for sleeping.
- Medify MA-25: a dimmer button.
- Alen BreatheSmart 35i: Auto Light Mode dims the control panel in a dark room. It dims rather than switching off.
Among the ones we left out, the Coway Airmega 100's sleep mode limits the buttons to half brightness, Rabbit Air's MinusA2 drops to dimmed sleep lighting, and IKEA's STARKVIND needs the IKEA Home app and the DIRIGERA hub to turn its LED off.
Auto modes that ramp up at night
Auto mode is the setting most likely to wake you. It raises the fan whenever the sensor sees worse air.
Winix says its Auto Mode runs low when air quality is good, medium when fair and high when poor. The 5510's automatic Sleep Mode has a second catch: the page says it returns to Auto Mode in the presence of light, so a bedside lamp or early daylight takes it out of its quietest speed.
Levoit's Core 400S manual shows the same pattern. The fan sits at its sleep speed when air quality reads very good and goes to high when it is bad. Levoit's app adds a Quiet Auto Mode that stops at medium speed, even when air quality is poor, "to avoid making too much noise". That is the only maker setting we found that caps an auto mode for noise.
Blueair, Alen and Coway all say their auto modes adjust the fan by air quality or particles.
The Levoit Core 200S-P and the Medify MA-25 have no auto mode in their manuals. For a bedroom, that is a plus: the fan stays where you put it.
Our advice is simple. Use auto during the day, if you like, and use the night or sleep setting, or a fixed low speed, when you go to bed. Levoit's manuals suggest running the top speed for 15 to 20 minutes before a lower one when there is a specific problem such as smoke. In a bedroom, do that while you are out of the room.
Where to put it
The makers ask for more space than a nightstand corner usually gives. Levoit asks for at least 15 inches of clearance on all sides. Medify asks for at least 20 inches between the air inlet and a wall or furniture. Winix asks for 12 to 18 inches from walls and says flimsy or slanted surfaces may cause abnormal noise and vibrations, so a hard, flat floor is better than a wobbly shelf.
What quiet costs in a bedroom
- Size. The unit with the most headroom, the Winix, is also the biggest: 22.17 inches tall and 13.3 lb. The Levoit Core 200S-P is 12.6 inches tall and 6.6 lb, but it is rated for only 140 sq ft.
- Airflow. The night setting moves a fraction of the rated air, so a small unit on its sleep speed may not keep up with a larger room.
- Big steps between speeds. The Medify jumps from 19.8 dBA on speed 1 to 37 dBA on speed 2. If speed 1 is not enough, the next step is more than twice as loud on the 10 dB rule.
- Price and filters. The Levoit is $89.99 with a $25.99 filter. The Alen is $289 with a $54 filter. The Medify's filters last 2,500 hours, about 3 to 4 months.
For more on the units, see dBA explained and why you cannot compare dB ratings across brands. For targets in other rooms, see how quiet is quiet enough, room by room.
How we chose
We started from the purifiers in our main guide and added the Levoit Core 200S-P because Levoit ties its low figure to its sleep mode. For each one we reopened the maker's product page and, where one is published, the manual, and recorded the noise figure in the maker's words with the setting it describes. We recorded room sizes at 4.8 air changes an hour, and CADR from the maker, AHAM Verifide or ENERGY STAR. We ranked for a bedroom: a figure tied to the night setting, room to spare for a 120 to 170 sq ft room, lights that go off or dim, and auto modes that stay out of the way.
We did not measure any of these purifiers ourselves. Every figure here comes from the maker's own page or manual, or from AHAM Verifide or ENERGY STAR, and no maker states the distance or standard behind its noise figure, so treat small differences as a tie.
