CADR Explained: How to Choose the Right Air Purifier for Your Room Size

CADR is one of the most useful numbers on an air purifier

Clean Air Delivery Rate, or CADR, is a measure of the volume of filtered air delivered by an air cleaner for particle removal. In simple terms, it helps answer a practical question: how quickly can this complete machine supply cleaner air to the room? That makes CADR more useful for room sizing than judging a purifier only by filter grade.

Why there can be several CADR numbers

AHAM's system reports CADR for tobacco smoke, dust and pollen, representing different particle-size ranges. Higher numbers indicate faster filtration for that category. For concern about fine particles, smoke CADR is particularly useful because smoke represents the smaller particle category in the rating system.

The AHAM two-thirds rule

AHAM recommends a simple rule of thumb: smoke CADR should be at least two-thirds of the room's area in square feet for a typical 8-foot ceiling. A 120-square-foot room, for example, would call for a smoke CADR of at least 80 cfm under this rule. A higher CADR simply means the purifier can clean the air more often or faster.

Using the rule in metric homes

Indonesian homes are normally measured in square metres, so the easiest approach is to convert the room area to square feet before applying the AHAM rule. One square metre is approximately 10.76 square feet. A 20 m2 room is about 215 square feet; two-thirds of that is roughly approximately 143 cfm (about 243 m³/h) smoke CADR. This is a rule of thumb, not a substitute for verified manufacturer sizing and local operating conditions.

Ceiling height matters

Room area alone assumes a standard ceiling height. EPA and AHAM both caution that higher ceilings mean more air volume, so a purifier rated for a larger room may be appropriate. Open-plan spaces also need to be considered as the full connected area the purifier is expected to serve.

Fan speed matters too

CADR is typically measured at the machine's highest speed. If you buy a unit whose highest setting is too noisy to use, your real-world clean-air delivery may be lower because you will operate it at a slower speed. This is why buying with some capacity margin can be sensible, especially for bedrooms where low noise is important.

CADR does not rate gas or odour removal

CADR is a particle-removal metric. It does not tell you how effectively a purifier removes odours, gases or VOCs. EPA recommends suitable activated carbon or other gas-phase media when gas removal is a goal, and notes that gas-filter performance does not have the same widely used consumer rating system as particle CADR.

One big purifier or multiple units?

If a home has separated rooms and closed doors, multiple correctly sized units can sometimes be more effective than expecting one purifier in the living room to clean bedrooms it cannot freely exchange air with. For a large open space, one high-CADR unit or multiple units may both be workable approaches depending on airflow, noise and placement.

What to look for on an AERAKAYU specification sheet later

When AERAKAYU models reach final qualification, WAZ Pure Living intends room-size guidance to be tied to verified clean-air performance rather than marketing-only coverage numbers. Until those specifications are final, we will not publish model-specific CADR or coverage claims.

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Sources & further reading

• AHAM Verifide — Air Filtration Standards - CADR definition and two-thirds sizing rule.
• U.S. EPA — Guide to Air Cleaners in the Home - CADR sizing table, high-ceiling guidance and gas-filtration limitations.