Updated: May 9, 2026.
Air Purifier Buying Basics
Start with the full HealthGlean bedroom air purifier guide, then use these explainers to size the purifier, evaluate filter claims, and avoid ozone mistakes.
CADR means clean air delivery rate. It is one of the most useful air-purifier numbers because it combines airflow and particle removal into a practical output: how much filtered air the machine delivers.
Room-size claims can be fuzzy, especially when brands use different air-change assumptions. For bedrooms, CADR is more useful than square footage alone because it helps you choose a purifier that can clean the room without needing to run loudly all night.
The Basic Sizing Rule
EPA says the CADR should be large enough for the room, and AHAM gives a simple rule of thumb: the CADR should be at least two-thirds of the room area in square feet. For wildfire smoke, AHAM recommends a smoke CADR equal to the room area.
| Bedroom Size | Room Area | Minimum CADR By 2/3 Rule | Stronger Smoke/Wildfire Target |
|---|---|---|---|
| 10 ft x 10 ft | 100 sq ft | About 65 cfm | About 100 smoke CADR |
| 10 ft x 12 ft | 120 sq ft | About 80 cfm | About 120 smoke CADR |
| 12 ft x 14 ft | 168 sq ft | About 112 cfm | About 168 smoke CADR |
| 14 ft x 16 ft | 224 sq ft | About 149 cfm | About 224 smoke CADR |
| 16 ft x 20 ft | 320 sq ft | About 213 cfm | About 320 smoke CADR |
Use Smoke CADR For Small Particles
Some labels show separate CADR numbers for smoke, dust, and pollen. EPA explains that tobacco smoke, dust, and pollen represent small, medium, and large particles. For fine particles and bedroom smoke concerns, smoke CADR is usually the most conservative number to compare.
Why Bedroom Sizing Needs A Buffer
- CADR is usually measured on high: a purifier that is barely adequate on high may be noisy on the setting you actually use for sleep.
- Ceiling height matters: EPA notes that rooms above 8 feet may need a larger purifier.
- Open doors change the room: an open bedroom door can make the purifier serve part of a hallway or living space.
- Filter age matters: airflow and performance can fall when filters are dirty or overloaded.
- Smoke events are different: wildfire smoke or heavy outdoor particle events call for more conservative sizing and public-health guidance.
Practical Formula
Measure length times width. Multiply the room area by 0.67 for a basic minimum CADR, then consider sizing up if you want quiet overnight operation, have high ceilings, pets, smoke exposure, or an open floor plan.
After sizing the room, use the HealthGlean bedroom air purifier guide to compare real product picks by CADR, low-speed noise, filter cost, and ionizer notes.
Sources And References
We checked these references on May 9, 2026. Product CADR, room-size claims, filter schedules, ionizer settings, and certification status can change, so verify the exact model before buying or replacing filters.
- EPA Guide to Air Cleaners in the Home
- AHAM air filtration standards and CADR sizing guidance
- EPA air cleaners, HVAC filters, and COVID-19 guidance
Informational note: This article is general education and shopping guidance, not medical advice. Air purifiers can support indoor-air control, but they do not replace source control, ventilation when outdoor air is clean, mold repair, smoke avoidance, or care from a qualified clinician for asthma, allergies, COPD, infection risk, or other respiratory concerns.