Room by Room · reference
Air Purifier for a Apartment: What Size You Need
for the largest room in a typical flat
EPA table, 500 sq ft row · 8-ft ceiling · minimums are per room
The flat is not the room. EPA’s minimums are published per room, so the sizing question is always "which room is this unit standing in?", not "how big is my home?" A flat’s main living space between the 300 and 500 sq ft rows takes 325 cfm.
One hallway unit cannot cover a flat. Doors close, air does not commute politely, and a machine sized to the total area is undersized everywhere at once. The honest plan is one unit per room that needs one.
Size the room, not the flat#
Take each room’s floor area, find its published row, round up between rows. A living room between the 300 and 500 sq ft rows takes 325 cfm; a bedroom between the 100 and 200 sq ft rows takes 130 cfm. The flat’s total area never enters the sum.
Each row is a per-room minimum at an 8-foot ceiling. An open-plan flat is the exception: one open stretch of floor is one zone, sized as a single room until it passes the table’s last row.
- 100 sq ft, 65 cfm
- 200 sq ft, 130 cfm
- 300 sq ft, 195 cfm
- 400 sq ft, 260 cfm
- 500 sq ft, 325 cfm
- 600 sq ft, 390 cfm
One unit per room, honestly#
Closed doors are real walls for air. The bedroom at night and the living room by day are separate sizing problems, and a unit in the hallway serves neither well.
If the budget allows one unit, put it in the room you use most, sized to that room. Add rooms as the budget allows. Units sized per room beat one heroic machine sized to the whole floor plan.
Suggested next step
Compare what the table asks for
Search listings for the published minimum your room needs, then check the smoke CADR on the shortlist before anything else.
Placement and running#
- Main room unit: open floor, clear of walkways, running during occupied hours.
- Bedroom unit: sized to the bedroom, run overnight on low.
- Kitchen: the range hood leads; a purifier catches what escapes.
- Hallway: under the smallest published row, honest, but it does not launder the other rooms’ air.
What the box leaves out#
A "whole-home coverage" claim is not a published figure. EPA’s table is per room; any promise to the contrary is a guess with a badge on it.
And the flat’s smells, cooking, bins, the neighbour’s cigarettes through the vents, are gases with no published CADR. The rated work is particles.
Questions people actually ask
Sources
- U.S. Environmental Protection Agency, Guide to Air Cleaners in the Home (2nd edition), retrieved 2026-08-30
Quoted and transcribed, never paraphrased into new numbers. This site does not interpolate between published figures.
Suggested next step
One more angle before you decide
The minimum is settled, spend the rest of the decision on noise, filter cost and the smoke CADR.
Get the next sizing brief
One email when a page earns its figure. No deal alerts, this site does not show prices.
Printed from https://roomandfilter.com/rooms/air-purifier-for-a-apartment, “Air Purifier for a Apartment: What Size You Need”. Figures from U.S. Environmental Protection Agency, Guide to Air Cleaners in the Home (2nd edition), retrieved 2026-08-30. No prices are shown on this site, by policy.