Breathe Naturally - January 2, 2024

Understanding the CADR Rating and Filter Efficiency


Key Takeways:

  • CADR stands for Clean Air Delivery Rate and measures airflow and particle removal.
  • Higher CADR ratings indicate better performance in cleaning the air.
  • Most quality air purifiers have a CADR of at least 300.
  • Filter efficiency refers to what percentage of particles are captured by a filter.
  • HEPA filters must have a minimum efficiency of 99.97% to qualify as True HEPA.
  • High efficiency filters like HEPA and activated carbon remove the most airborne contaminants.

When choosing an air purifier, two key specifications to consider are the CADR rating and filter efficiency. Understanding these metrics helps identify models that will effectively clean your interior air. CADR relates to the unit’s cleaning power, while filter efficiency indicates how well the filters trap particles.

What is CADR?

CADR stands for Clean Air Delivery Rate. This important rating measures an air purifier’s delivery of contaminant-free air, indicating its overall cleaning performance. Specifically, the CADR rating designates the cubic feet per minute (CFM) of purified air produced by the unit. Models with higher CADR ratings clean more air per minute.

CADR takes into account both the airflow volume as well as the particle removal efficiency. Air purifiers are tested with three particle types - tobacco smoke, pollen and dust. Performance ratings are provided for each contaminant type. For example, an air purifier with a dust CADR of 250 means it produces 250 cubic feet of dust-free air each minute. Overall CADR combines the results of all three tests into a single number.


A higher quality of air for the ones you love

Recommended CADR Levels

When deciding which CADR numbers to look for, match the rating to the room size needing purification. Higher CADR models clean the air faster but also cost more. The minimum recommended CADR levels are:

• 100-150 for small rooms up to 100 sq ft
• 200-300 for mid-sized rooms of 200 sq ft
• 300+ for large rooms including open concept spaces

Models with a CADR over 300 provide the fastest air purification, while still being cost effective for most homeowners compared to commercial-grade systems.

What is Filter Efficiency?

Filter efficiency expresses what percentage of particles are captured by the air filter. Most filters have a minimum efficiency reporting value (MERV) between 1 and 16 - the higher the better. However, specialized filters like HEPA and ULPA are rated differently.

HEPA filters must meet a 99.97% standard to qualify as True HEPA. This means particles as small as 0.3 microns are filtered at this efficiency. ULPA (ultra low penetration air) filters take it further with 99.9995% efficiency for particles right down to 0.1 microns.

Activated carbon filters also trap microscopic particles through the adsorptive process. And they contain pores for capturing gases, smoke and odors. When used along with HEPA filters, activated carbon provides comprehensive contaminant removal.


The Bottom Line

Checking a purifier's CADR rating along with the grade of filters used gives a complete picture of its purification capabilities. Models with both high CADR over 300 and True HEPA filters provide superior air cleaning power for most homes. Understanding these specifications makes it easier to shop for a unit that best fits your space and indoor air quality needs.


Environmental Protection Agency. "Guide to Air Cleaners in the Home." Accessed November 20, 2023.

American Lung Association. "Residential Air Cleaning Devices."