What smoke CADR does my room need?

NEA’s air pollution FAQs (last updated 22 October 2026) give the minimum smoke CADR (Clean Air Delivery Rate) that a portable air cleaner’s filters should provide, in m³/h, which NEA also writes as cmh: smoke CADR effected by air filters ≥ room size (m³) × 5. NEA gives the room size in m³, so it is the room’s volume: multiply the length, width and height, then multiply by 5. NEA recommends more in three cases: in spaces where ventilation cannot be easily improved (NEA’s example is no operable windows), in spaces with high-risk activities, or if the air cleaner contains electronic air-cleaning technologies. There the rule is overall smoke CADR ≥ room size (m³) × 7. The CADR calculator above works out both.

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 5 is 124.8, so at least 125 m³/h once rounded up. Times 7 is 174.72, so at least 175 m³/h if one of NEA’s three cases applies.

What examples does NEA give for an HDB flat?

NEA says that for a typical bedroom (10–12 m²) in a 4-room HDB flat, air purifiers should have a smoke CADR of approximately 130–156 m³/h or higher, and for a typical living room (20–25 m²) approximately 260–325 m³/h or higher, depending on room size. Those room sizes are floor areas, not volumes. Our reading, not NEA’s statement: the figures match the standard rule with a 2.6 m ceiling (10 m² × 2.6 m × 5 = 130; 25 m² × 2.6 m × 5 = 325). NEA does not say what ceiling height it assumed, so measure your own room’s height and use the calculator rather than the floor area alone.

Which number on the label do I compare?

Compare the smoke CADR on the label with your figure, in m³/h, the unit NEA now uses. If a label gives CADR in cubic feet per minute (CFM), it is in a different unit: 1 CFM is about 1.7 m³/h (our conversion, from 0.3048 m per foot and 60 minutes per hour). NEA’s standard minimum is for smoke CADR “effected by air filters” and its higher one is for “overall” smoke CADR; if a label does not make clear which its figure is, ask the supplier. NEA’s air cleaning devices page defines CADR as the amount of clean air a device can produce for a room, says a higher CADR indicates greater ability to return clean air to the room, and advises buyers to speak with suppliers to obtain detailed product information on suitability. The FAQs also say highly efficient filters, such as HEPA filters, are preferred for removing fine particles.

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 does not decide which of NEA’s two figures applies to your room: that depends on your ventilation, what happens in the room and the unit’s technology, which NEA leaves to you. 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’s formulas are minimums, 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?

On NEA’s standard rule, a smoke CADR from the air filters of at least 5 × 30 = 150 m³/h (our illustration: a 4 m by 3 m room with a 2.5 m ceiling). Where ventilation cannot be easily improved, where there are high-risk activities, or if the unit contains electronic air-cleaning technologies, NEA recommends an overall smoke CADR of at least 7 × 30 = 210 m³/h.

Why is the figure higher than it used to be?

NEA changed the rule in its air pollution FAQs on 22 October 2026. The page used to say a smoke CADR of at least 3 times the room’s volume in cubic metres, or 1/12 of the volume in cubic feet, with no unit. It now gives at least 5 times the volume in m³, in m³/h, as the standard minimum, and 7 times in three cases it names. The calculator follows the current wording.

What unit is the CADR in?

NEA’s FAQs give smoke CADR in m³/h, which they also write as cmh (cubic metres per hour). A figure in cubic feet per minute needs converting first: 1 CFM is about 1.7 m³/h (our conversion).

What if my air purifier has no CADR rating?

NEA’s sizing rule is written in smoke CADR, so without one you cannot apply it directly. NEA’s air cleaning devices page advises buyers to speak with suppliers to obtain detailed product information on whether a unit suits their household.

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