EN
English中文Bahasa MelayuBahasa Indonesia

Air purifier size calculator for haze (HDB rooms)

For haze, choose a HEPA purifier whose smoke CADR is at least five times the room's volume per hour: about 130 m³/h (77 CFM) for a 10 m² bedroom with a 2.6 m ceiling. That matches the US EPA rule of thumb of a smoke CADR of at least two-thirds of the floor area in square feet. Keep doors and windows closed while it runs.

Room sizes are typical; check your floor plan or measure for a closer answer.

Minimum smoke CADR for this room

130 m³/h (77 CFM)

Floor area 10 m²×Ceiling 2.6 m=Room volume 26.0 m³×Air changes 5=CADR 130 m³/h

US EPA rule of thumb (two-thirds of the floor area in ft²): 72 CFM (122 m³/h)

Is my purifier enough?

Printed on the box or spec sheet, often as 'CADR (smoke)' or 'CADR for particles'.

How the number is worked out

Room volume = floor area × ceiling height. Required CADR = volume × air changes per hour. Five air changes an hour is about the same as the US EPA rule of thumb for a standard ceiling.

1 CFM (cubic foot per minute) = 1.699 m³/h. Makers in Asia usually quote m³/h; US brands quote CFM.

Getting the most from a purifier during haze

  • Use the smoke CADR, not a 'suitable room size' figure that does not say how many air changes it assumes.
  • Close windows and doors, and run it on a high setting: low settings deliver far less clean air.
  • A true HEPA filter removes fine smoke particles; an activated-carbon layer helps with the burning smell, which HEPA alone does not remove.
  • Avoid ozone generators and devices that give off ozone: ozone irritates the lungs.
  • One purifier cleans one room. If you have one, put it in the bedroom where the most vulnerable person sleeps.
  • Check the filter more often during haze: heavy smoke clogs it sooner than the maker's normal schedule.

Quick answers

What size air purifier do I need for a 25 m² living room?

About 325 m³/h (191 CFM) of smoke CADR, assuming a 2.6 m ceiling and five air changes an hour. If no single unit reaches that, use two smaller ones or keep the purifier in a bedroom instead.

What does CADR mean?

Clean air delivery rate: how much filtered air a purifier delivers, in m³ per hour or cubic feet per minute. It is measured separately for smoke, dust and pollen; for haze, use the smoke figure.

Should I run my air purifier all day during haze?

Run it whenever the outdoor 1-hour PM2.5 is above 55 µg/m³ and the room is in use, especially overnight in bedrooms, with windows closed.

Related questions

References

  1. Indoor air filtration factsheet. US Environmental Protection Agency, 2026.
  2. Guide to Air Cleaners in the Home. US Environmental Protection Agency.

Sources

Cite this page

Haze Day. “Air purifier size calculator for haze (HDB rooms).” haze.day, updated . https://haze.day/en/tools/air-purifier

Licensed CC BY 4.0: free to quote and reuse with credit and a link. HTML link:

<a href="https://haze.day/en/tools/air-purifier">Air purifier size calculator for haze (HDB rooms)</a> (Haze Day)

General information, not medical advice. Follow your doctor and your school, league or organiser's final call. Data come from official sources; see data sources.