What smoke CADR does my room need?

NEA’s air pollution FAQs say an appropriate air purifier should have a smoke CADR (Clean Air Delivery Rate) number of at least 3 times the volume of the room in cubic metres, or 1/12 of the volume of the room in cubic feet. Multiply the room’s length, width and height to get its volume, then apply either form: the CADR calculator above does both. NEA’s page gives no unit for the CADR number, so match the unit on the label or ask the supplier before you compare. NEA’s sentence puts “at least” before the first form only; reading it as covering both is ours.

Our illustration, not NEA’s example: a 3.2 m by 3.0 m bedroom with a 2.6 m ceiling is 24.96 m³. Times 3 is 74.88, so the metric form asks for at least 75 once rounded up. In cubic feet the room is about 881.5 ft³, and 881.5 ÷ 12 is about 73.5.

Why does the calculator show two figures?

NEA prints the rule in two forms and names no unit for either, so the tool shows both side by side instead of choosing one. Our reading, not NEA’s statement: the two forms give about the same figure, about 2% apart, because 1 m³ is about 35.3 ft³ and 35.3 ÷ 12 is about 2.94, close to 3. If that reading is right they describe one CADR figure, but NEA does not say so, which is why the tool never converts a label’s CADR from one unit to another. If a label’s unit is unclear, ask the supplier: NEA’s air cleaning devices page advises buyers to speak with suppliers to obtain detailed product information on suitability.

Which number on the label do I compare?

NEA says a CADR label has three numbers, one each for smoke, dust and pollen, and that the smoke CADR is the most appropriate for haze pollutants. NEA also says many effective air purifiers have no CADR rating, and that users should obtain from the manufacturer information that backs any claim about how well a unit removes fine particles. The air cleaning devices page defines CADR as the amount of clean air a device can produce for a room.

What does this calculator not do?

It does not recommend, rate or name any purifier, and it does not say whether you need one. It treats the room as one enclosed, box-shaped space, so an open-plan area, a high void or a sloping ceiling needs your own judgement, and NEA’s page does not cover those cases. NEA says “at least”, so your figure is a floor, and the page does not say how far above it to go. The tool rounds the figure up to a whole number, which is our convention, and it gives no health advice.

Our guide to choosing an air purifier by CADR covers what else to ask a seller. The appliance running cost calculator turns a purifier’s watts and hours into dollars, and a simple product brief is a place to write down your minimum CADR before you shop.

What CADR do I need for a 30 m³ room?

NEA’s metric form asks for at least 3 times the volume in cubic metres, so 90 for 30 m³ (our illustration: a 4 m by 3 m room with a 2.5 m ceiling). In cubic feet that room is about 1,059 ft³, and 1,059 ÷ 12 is about 88. NEA names no unit, so check the unit on the label.

Does NEA say what unit CADR is measured in?

No. The sentence in NEA’s air pollution FAQs gives bare numbers: at least 3 times the room volume in cubic metres, or 1/12 of the volume in cubic feet. Match the unit on the label, or ask the supplier.

What if my air purifier has no CADR rating?

NEA says many effective air purifiers have no CADR rating and that users should obtain from the manufacturer information backing any claim about removing fine particles. Without a CADR you cannot apply the room-size rule directly.

Is anything I type sent anywhere?

No. The sum is worked out in your browser.

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