A purifier in a home office has a different job from one in a bedroom. It runs through the working day, while you type, think and talk on video calls, a few feet from a microphone. You will not run it on its sleep setting. You will run it on the speed you can live with all day, which for most people is the medium or second speed.
That is the figure makers rarely print. Our main guide to the quietest air purifiers explains why the airflow rating describes the top speed and the quiet figure the bottom one. This guide looks at the middle: who publishes a figure for it, how much air that speed moves, which auto modes ramp up during a call, where to put the unit, and what filters cost when the purifier only runs during office hours. We make no health claims, and we have left the makers' health claims out.
Our picks are listed above, with full specifications for each.
The speed you actually run in an office
In a bedroom, the setting that matters is the night or sleep mode. Our bedroom air purifier guide covers that. In an office the room is busier: a computer fan, a keyboard, a street outside, and your own voice. The National Institute on Deafness and Other Communication Disorders puts normal conversation at 60 to 70 dBA, a humming refrigerator at 40 dB and whispering at 30 dB. A purifier at 20 dB on its slowest speed is quieter than a whisper, but at that speed it moves only a small share of its rated air, so in a working office you will turn it up.
Every maker we read publishes a low figure. Few publish anything in between. Of the purifiers in our catalog, only Medify lists a figure for every speed, and IQAir does it for its Atem Desk. Alen publishes airflow at every speed but noise only at the two ends. Levoit, Coway and Winix print a range or a single low figure.
So we rank only where the figures allow it. Four Medify units list a figure at Speed 2 in dBA, and Medify's manuals label every one of them "dBA sound pressure":
- MA-50 V3.0: 32.3 dBA at Speed 2, the second of four speeds
- MA-25: 37 dBA at Speed 2, the medium of three
- MA-14: 37.2 dBA at Speed 2, which its manual calls medium
- MA-40: 50.3 dBA at Speed 2, the medium of three
The MA-25 and MA-14 are a tie: two tenths of a decibel tells you nothing when no distance is stated. The MA-50 is lowest, but note that its Speed 2 is the second of four speeds, not the middle of three. It is the same label and unit, and the airflow at that speed, below, shows what it buys.
The IQAir Atem Desk lists 27 at Speed 2, lower than any of them. IQAir's technical sheet calls its figures "Sound power level", which describes the machine itself rather than the sound at a listening position. Sound power and sound pressure are different quantities, and our explainer on sound power vs sound pressure shows why one cannot be read as the other. We list the Atem Desk, but we do not rank it against the Medify figures.
How much air the middle speed moves
A quiet speed that does not clean the room is no use. Two Medify models publish the CADR at every speed, which lets you see what each step buys:
- MA-50 V3.0: Speed 1, 19.0 CFM at 21.2 dBA; Speed 2, 90.6 CFM at 32.3 dBA; Speed 3, 159.5 CFM at 42.7 dBA; Speed 4, 352 CFM at 60.6 dBA.
- MA-40: Sleep Mode, 111.8 CFM at 40.5 dBA; Speed 1, 144.3 CFM at 40.5 dBA; Speed 2, 181.2 CFM at 50.3 dBA; Speed 3, 239 CFM at 53.3 dBA.
Alen publishes airflow, not CADR, by speed for the BreatheSmart 35i: 66, 98 and 135 CFM, then 190 on Turbo. IQAir lists 4.7, 8.8 and 18 cfm for the Atem Desk.
AHAM's rule of thumb is that the smoke CADR should be at least two-thirds of the room's floor area. The EPA says CADR is typically measured at the highest speed, so the rule is written for the top-speed rating. If you apply the same rule to the speed you actually run, which is our own extension of it, a typical office needs:
- 100 sq ft: about 67 CFM
- 120 sq ft (10 by 12): about 80 CFM
- 150 sq ft: about 100 CFM
- 200 sq ft: about 133 CFM
- 300 sq ft: about 200 CFM
On those numbers, the MA-50 V3.0 covers a 120 sq ft office at Speed 2, 32.3 dBA, and a 200 sq ft office at Speed 3, 42.7 dBA. A 300 sq ft office is harder. The MA-50 reaches 200 CFM only at Speed 4, 60.6 dBA, and the MA-40 at Speed 3, 53.3 dBA. Neither is quiet enough to sit through a call. For a big office or a converted garage, see our large-room purifier guide, and accept that the purifier may need to run hard when you are not talking.
The jump between speeds matters as much as the figure. The National Park Service says every 10 decibels is a doubling of perceived loudness. The MA-50's step from Speed 2 to Speed 3 is 10.4 dBA, so on that rule Speed 3 sounds about twice as loud. The MA-25's step from Speed 1 to Speed 2 is 17.2 dBA. If Speed 1 is not enough, the next setting is a big change.
Auto modes that ramp up mid-call
Auto mode is the setting most likely to be heard on a call. It raises the fan whenever the sensor sees worse air, and in a house that can be someone cooking downstairs or dust stirred up in the next room.
- Levoit Core 300S-P: the manual's chart runs from Sleep Mode in very good air to High in bad air. The VeSync app adds a Quiet Auto Mode that "never uses the highest fan speed to avoid making too much noise." Our Levoit air purifier decibels page lists which other Levoit models have it.
- Levoit Vital 100S-P: its manual says "Auto Mode does not use the turbo fan speed".
- Alen BreatheSmart 35i: adjusts its speed automatically from an air quality sensor. Our Alen decibels page lists every Alen model's two published ends.
- Medify MA-14, MA-25, MA-40 and MA-50 V3.0: no auto mode is listed in their controls. The fan stays where you put it.
- IQAir Atem Desk: no air quality sensor. Its app can switch it on and off by sensing your phone nearby.
Our advice is to use a fixed speed during working hours and to save auto, or a full-speed burst, for when you are out of the room.
Two smaller sounds are worth knowing about. The Atem Desk's user guide says that with every touch to change speed, "you will hear a sound and see the light change", although its app has light and sound settings. Medify's MA-40 manual says the unit beeps when it is plugged in. Neither matters if you set the speed before the call starts.
Where to put it: away from the desk and the microphone
The simplest way to make a purifier quieter on a call is distance. OSHA's technical manual explains that in open space sound falls by about 6 decibels for every doubling of distance, but that indoors it falls more slowly, because it reflects off walls and surfaces. A small office with a hard desk and bare walls keeps more of the sound, so put the purifier as far from the microphone as the room allows.
The makers also ask for space around the unit. Medify's manuals ask for at least 20 inches between the air inlet and a wall or furniture. Levoit asks for 15 inches of clearance on all sides. So a purifier pushed under the desk or into a corner beside it is wrong for two reasons: it is close to the microphone, and it is short of air.
Desk units are the awkward case. IQAir tells you to put the Atem Desk "as close to you as possible" and to point it at your breathing zone. That is the point of a personal purifier, and it is also the worst place for a microphone. If you buy one, test a recording at the speed you plan to use. The same reasoning applies to a desk fan; our guide to the quietest desk fans covers which fan makers publish a figure for each speed.
For the rest of the room, our page on setting up a quiet home office covers computers, printers, shredders and the other machines that share the space.
Compact units and floor units
The smaller units are easier to find a place for, but they give up airflow:
- Medify MA-14: 12.2 inches tall, rated for 89 sq ft on its page and 117 sq ft in its manual.
- Medify MA-25: 13.5 inches tall, rated for 172 sq ft.
- Levoit Core 300S-P: 14.2 inches tall, rated for 219 sq ft.
- Medify MA-50 V3.0: 21.18 inches tall, rated for 550 sq ft.
- Alen BreatheSmart 35i: 20.6 inches tall, 233 sq ft on its ENERGY STAR listing.
The bigger unit is the quieter choice in most offices, because it can run on a lower speed and still keep up. A small unit in a 200 sq ft room will spend the day near its top speed.
What filters cost at office hours
Makers quote filter life in different ways, and for an office the basis matters.
- Medify rates its filters at 2,500 hours and calls that 3 to 4 months, which only works out if the purifier runs around the clock. Eight hours a day, five days a week, is about 2,080 hours a year by our arithmetic. On that basis a Medify filter lasts a little over a year in an office that is only used during the workday. The filters cost $39.99 for the MA-14, $49.99 for the MA-25 and $69.99 for the MA-50 V3.0.
- Alen quotes 9 to 12 months for the 35i's $54 Essential filter, at 24/7 operation.
- Levoit says the Core 300S-P filter should be replaced every 6 to 8 months, and that you may need to replace it earlier or later depending on how often you use the purifier. It costs $29.99.
- IQAir says the Atem Desk filter lasts about a year at 10 hours a day on Speed 3, and sells it for $79.99.
That makes the Levoit cheapest to run on paper, and the Medify units cheaper in an office than their 3 to 4 month interval suggests.
Mistakes to avoid
Buying on the lowest figure. The figure at the speed you run is the one your microphone hears.
Ranking across quantities. IQAir's 27 is sound power; Medify's 32.3 is sound pressure. See dBA explained for what the A-weighting does and does not tell you.
Sizing to the room exactly. A unit rated for exactly your floor area will run on its loud speeds.
Leaving auto on through calls. It will follow the air up to high.
Trusting one document. Medify's MA-14 page and manual disagree on room size, CADR and weight, and Levoit's Core 300S-P page and manual disagree on the top figure. We quote both where they differ.
How we chose
We started from the purifiers in our main and bedroom guides and searched for makers that publish a figure at a named middle speed. Medify does for every model we read, and IQAir does for the Atem Desk; we added four of those units to our catalog. For each pick we reopened the maker's product page and, where one is published, the manual or technical sheet, and recorded the noise figure in the maker's words with the speed it describes. We ranked by the figure at Speed 2 only within one group, Medify's dBA sound pressure figures, and gave credit to makers that publish airflow or CADR by speed.
We did not measure any of these purifiers, or record any of them through a microphone. Every figure comes from the maker's own page, manual or technical sheet, or from AHAM Verifide or ENERGY STAR as the maker or listing reports it, and no maker states the distance behind its noise figures, so treat small differences as a tie.
