This guide shows how to size an air purifier for an open-plan home, where the living room runs into the dining area, kitchen or staircase with no doors between them. It covers how to measure the space, how much clean air you need, and when one big purifier beats two smaller ones.
Why open-plan rooms need different sizing
A purifier cleans all the air it can reach, not just the room you think of as the living room. In a closed bedroom that is easy: the walls and door set the space. In an open-plan home the air moves freely into the dining area, the kitchen and up the stairs, so the purifier is really working on all of it.
So the first rule is simple: measure every area that is open to the room, not only the part with the sofa. A 300 sq ft living room that opens into a 200 sq ft dining area and a 100 sq ft kitchen is a 600 sq ft space for the purifier. The US EPA’s guide to air cleaners says the same: in an open floor plan, size for the whole area the air cleaner has to serve.
How to measure an open-plan space
- Add up the floor area of every connected part with no door: living, dining, open kitchen, hallway. Length times width in feet gives sq ft.
- Check the ceiling height. Most rooms are about 8 to 9 ft. A double-height living room or an open staircase means much more air.
- Note the shape. A simple rectangle is easy for one purifier. An L-shape or a long room with a partial wall is harder.
- Find where dirty air comes in: balcony doors, a main door that opens onto the road, a kitchen window.
How much clean air an open-plan room needs
CADR (Clean Air Delivery Rate) is the amount of clean air a purifier puts out each hour. AHAM, which runs the CADR test, gives a simple rule: a smoke CADR, in cubic feet per minute, of at least two-thirds of the floor area in sq ft. In the units we use, that is about 1.13 m³/h of smoke CADR for every sq ft of floor. The rule assumes a ceiling of about 8 ft. For higher ceilings, both AHAM and the EPA say to choose a purifier rated for a bigger room, and the EPA says to use more than one purifier when one cannot cover the area.
Here is the arithmetic for the 600 sq ft example:
| Open-plan space | Smoke CADR needed | What covers it |
|---|---|---|
| 600 sq ft, 8 ft ceiling | 600 x 2/3 = 400 cfm, about 680 m³/h | One HealthProtect 7770i (735 m³/h) |
| 600 sq ft, 10 ft ceiling | 680 x 10/8 = about 850 m³/h | Two Blue 3610 (600 + 600 = 1,200 m³/h) |
| 900 sq ft L-shape, 8 ft ceiling | 900 x 2/3 = 600 cfm, about 1,020 m³/h | Two Blue 3610, one in each arm of the L |
Smoke CADR figures are from our product pages, which use Blueair’s published ratings. For the full method, including air changes per hour, read our CADR and room size guide.
One large purifier or two smaller ones?
One large purifier is the simpler choice for an open rectangle with a normal ceiling. Two smaller ones work better when the clean air cannot reach every corner from one spot.
| One large purifier | Two smaller purifiers | |
|---|---|---|
| Best for | Open, simple rectangle | L-shapes, long rooms, partial walls, high ceilings |
| Placement | One good central spot needed | One unit in each zone |
| Noise | May need a higher speed | Each can run slower and quieter |
| Filters | One filter to change | Two filters to change |
| Flexibility | Stays in one room | Move one to a bedroom at night |
The running cost is close. Our product pages put a HealthProtect 7770i at about Rs 3,914 a month and a Blue 3610 at about Rs 2,170 a month, counting a filter change every 6 months and 8 hours a day on full speed at Rs 9.50 a unit. Two Blue 3610 units come to about Rs 4,340 a month and give more clean air in total. For the electricity side, see what an air purifier costs to run in Nepal.
Choose two units when the room looks like this
- The room is an L-shape, or the dining area sits around a corner from the living area.
- A partial wall or a big shelf unit splits the space.
- The only spot for a purifier is at one end of a long room.
- The ceiling is double height, or a staircase opens into the room.
- Balcony doors at one end and a main door at the other let dust in from two sides.
Where to put it in an open-plan room
Put the purifier where air can flow freely all around it, in the part of the room where people sit, not behind the sofa or pushed into a corner. If dust comes in mostly from one door, a spot between that door and the seating area works well. With two units, put one in each zone. Our guide on where to put an air purifier covers placement in detail.
Open kitchens and open staircases
A purifier in an open-plan living room will catch cooking smoke that drifts in, but it does not replace an exhaust fan or chimney hood over the stove. Catch the smoke at the stove first; see our guide to cooking smoke and odour.
An open staircase connects the living room to the floor above, so the air mixes between floors. One purifier downstairs will not clean the bedrooms upstairs well. Read whether one air purifier can clean a whole house before you plan for two floors.
Blueair purifiers for open-plan rooms
These in-stock models suit open-plan spaces. Room sizes and CADR are from our product pages, based on Blueair’s ratings.
| Model | Room size | CADR (smoke) | Best open-plan use |
|---|---|---|---|
| HealthProtect 7770i | Up to 674 sq ft | 735 m³/h | One unit for a large open living and dining area |
| Blue 3610 | Up to 549 sq ft | 600 m³/h | A medium open space, or two units for an L-shape or high ceiling |
The HealthProtect 7770i changes the air in 674 sq ft about every 12.5 minutes, has Wi-Fi and Auto mode, and comes with a 3-year warranty handled in Nepal. The Blue 3610 does the same for 549 sq ft and runs at 23 dB(A) on its lowest speed. Both use Blueair’s HEPASilent filtration, which captures 99.97% of particles down to 0.1 micron. For more picks, see our large room air purifier page.
Open-plan air purifier: FAQs
What size air purifier do I need for an open-plan living room?
Add up the floor area of every connected part with no door between them, then aim for a smoke CADR of about 1.13 m³/h per sq ft. A 600 sq ft open space with a normal ceiling needs about 680 m³/h.
Is one big air purifier better than two small ones?
For a simple open rectangle, one big unit is easier. For an L-shape, a long room or a high ceiling, two units placed in different zones clean the air more evenly.
Can I add the CADR of two purifiers together?
Yes, if they serve the same connected space. Two Blue 3610 units give about 1,200 m³/h of smoke CADR between them.
Can an air purifier clean the kitchen in an open-plan room?
It catches cooking smoke that drifts into the living area, but use an exhaust fan or hood at the stove for the smoke itself.
