When shopping for an air purifier, you’ll likely encounter the term “CADR rating” on product packaging and in specifications. CADR (Clean Air Delivery Rate) is a standardized measurement system that indicates how effectively an air purifier filters specific airborne particles. Established by the Association of Home Appliance Manufacturers (AHAM), this rating helps consumers compare different air purifiers objectively. Understanding CADR ratings is essential for selecting the right air purifier that matches your specific room size and air quality concerns.
CADR stands for Clean Air Delivery Rate, a metric that measures an air purifier’s effectiveness in removing airborne pollutants from a room. Developed by the Association of Home Appliance Manufacturers (AHAM), CADR provides an objective standard for comparing different air purifier models.
Unlike simple airflow measurements, CADR considers both the volume of air processed and the efficiency of the filtration system. The rating is expressed in cubic feet per minute (CFM), indicating how many cubic feet of filtered air the purifier delivers each minute.
CADR specifically measures the removal of three common pollutants: smoke (particles 0.09-1.0 microns), dust (particles 0.5-3.0 microns), and pollen (particles 5.0-11.0 microns). Each pollutant receives its own CADR value, reflecting how efficiently the air purifier removes that particular contaminant.
How CADR Ratings Are Measured
AHAM conducts CADR testing in a controlled chamber measuring 1,008 cubic feet (equivalent to a 12′ x 12′ room with 7′ ceilings). Technicians introduce specific amounts of smoke, dust, and pollen into the chamber and measure how quickly the air purifier removes these contaminants compared to natural air settling.
The testing process is rigorous and standardized. Technicians first measure the natural decay rate of particles without an air purifier. Then, they run the same test with the air purifier operating at its highest speed. The difference between these measurements, after accounting for the room size, determines the CADR rating.
CADR ratings typically range from 0 to 450 CFM, with higher numbers indicating better performance. Most residential air purifiers have CADR ratings between 100 and 400 CFM. The measurement is precise enough to allow for meaningful comparisons between different models.
CADR Testing Limitations
While comprehensive, CADR testing has some limitations. Tests are conducted with brand new filters at maximum fan speed, which may not reflect real-world usage. Additionally, the testing period is relatively short (20 minutes), so long-term performance isn’t evaluated. The test also doesn’t account for gaseous pollutants like VOCs or odors.
Interpreting CADR Numbers
Understanding what CADR numbers mean is crucial for selecting the right air purifier. In general, higher CADR values indicate better performance, but what constitutes a “good” rating depends on your room size and specific needs.
For average-sized rooms (about 300 square feet), look for CADR ratings of at least 200 for smoke, 200 for dust, and 180 for pollen. For larger spaces or areas with significant air quality challenges, aim for higher ratings. For small spaces like bedrooms, a CADR of 100-150 may be sufficient.
| Room Size (sq ft) | Recommended Minimum CADR | Ideal for |
|---|---|---|
| 100-200 | 65-130 | Small bedrooms, offices |
| 200-300 | 130-195 | Large bedrooms, small living rooms |
| 300-400 | 195-260 | Master bedrooms, medium living rooms |
| 400-600 | 260-390 | Large living rooms, open floor plans |
To determine the appropriate CADR for your space, you can use the two-thirds rule: the CADR rating should be at least two-thirds of your room’s square footage. For example, a 300 square foot room would need an air purifier with a CADR of at least 200.
The Three CADR Measurements Explained
CADR ratings are provided separately for three different types of particles, each representing common indoor air pollutants with different particle sizes:
- Smoke CADR: Measures removal of small particles (0.09-1.0 microns), including cigarette smoke, cooking smoke, and combustion particles. This is often the most challenging rating for purifiers to score well on.
- Dust CADR: Evaluates removal of medium-sized particles (0.5-3.0 microns), including household dust, pet dander, and dust mite debris. This is particularly important for allergy sufferers.
- Pollen CADR: Assesses removal of larger particles (5.0-11.0 microns), such as pollen from trees, grasses, and weeds. This rating matters most for seasonal allergy sufferers.
Most air purifiers perform better with larger particles, so you’ll typically see higher CADR ratings for pollen than for smoke. When evaluating an air purifier, pay special attention to the CADR that addresses your primary concern.
Limitations of CADR Ratings
While CADR ratings are valuable, they don’t tell the complete story about an air purifier’s performance. Several important factors aren’t captured in the CADR system:
- Noise levels at different operating speeds
- Energy efficiency and operating costs
- Filter lifespan and replacement costs
- Gaseous pollutant removal (VOCs, odors, gases)
- Long-term performance as filters age
- Smart features and usability
Additionally, CADR tests are performed with the air purifier running at maximum speed, which might be too loud for everyday use. At lower, more practical speeds, the effective CADR will be reduced. Some high-end purifiers with advanced technology might perform better in real-world conditions than their CADR ratings suggest.
CADR Ratings Compared to Other Air Purifier Metrics
CADR is just one of several metrics used to evaluate air purifiers. Understanding how it relates to other common specifications can provide a more comprehensive assessment of an air purifier’s capabilities.
| Metric | What It Measures | Importance |
|---|---|---|
| CADR | Effectiveness in removing specific particles | Primary indicator of cleaning performance |
| ACH (Air Changes per Hour) | How many times the air in a room is filtered per hour | Indicates speed of air cleaning; higher is better |
| Filter Type (HEPA) | Filtration efficiency by particle size | Indicates the smallest particles that can be captured |
| Coverage Area | Maximum room size recommended by manufacturer | Often optimistic; use CADR-based calculations instead |
| Energy Consumption (Watts) | Power usage | Impacts operating costs and sustainability |
While HEPA filters are required to remove 99.97% of particles at 0.3 microns, the CADR tells you how much clean air is being produced. An air purifier with a lower-grade filter but a powerful fan might have a higher CADR than one with a better filter but weaker airflow.
The Relationship Between CADR and ACH
Air Changes per Hour (ACH) indicates how many times the purifier can process all the air in a room every hour. For example, an ACH of 5 means the entire room’s air is filtered five times per hour. Higher ACH rates lead to faster air cleaning.
You can calculate the ACH using the CADR rating with this formula: ACH = (CADR × 60) ÷ (room volume in cubic feet). For allergy and asthma sufferers, an ACH of at least 4-5 is recommended for effective relief.
Top Air Purifiers by CADR Rating
To help you compare models, here’s a table of popular air purifiers with their respective CADR ratings and approximate price ranges. These represent some of the highest-performing options on the market as of 2023:
| Model | Smoke CADR | Dust CADR | Pollen CADR | Recommended Room Size | Price Range |
|---|---|---|---|---|---|
| Coway AP-1512HH Mighty | 233 | 246 | 240 | 361 sq ft | $200-$230 |
| Blueair Blue Pure 211+ | 350 | 350 | 350 | 540 sq ft | $300-$340 |
| Honeywell HPA300 | 300 | 320 | 300 | 465 sq ft | $220-$250 |
| Levoit Core 400S | 260 | 273 | 280 | 403 sq ft | $220-$250 |
| Winix 5500-2 | 232 | 243 | 246 | 360 sq ft | $160-$200 |
| Medify MA-40 | 380 | 380 | 400 | 590 sq ft | $270-$300 |
Notice that higher CADR ratings generally correlate with higher prices, though there are exceptions that offer excellent value. The recommended room size is calculated using the two-thirds rule applied to the lowest CADR rating (typically smoke).
How to Use CADR Ratings When Shopping
To make the most of CADR ratings when purchasing an air purifier, follow these practical shopping guidelines:
- Measure your room’s square footage first (length × width)
- For standard ceiling heights (8 feet), use the two-thirds rule: minimum CADR should be at least 2/3 of your room’s square footage
- For rooms with higher ceilings, adjust upward accordingly
- Focus on the CADR rating for your primary concern (smoke for general air quality, dust for allergies, pollen for seasonal allergies)
- Look for the AHAM Verified seal, which guarantees the ratings have been independently tested
- Don’t rely solely on manufacturer claims about room coverage; verify with CADR calculations
Beware that some manufacturers may highlight only their highest CADR rating (usually pollen) or use non-standard measurements. Always look for the separate ratings for smoke, dust, and pollen. Some brands might use different metrics if their CADR ratings aren’t competitive.
Common CADR Misconceptions
There are several misconceptions about CADR ratings that can lead to poor purchasing decisions:
- Myth: Higher price always means higher CADR. Reality: Some moderately priced units outperform premium models in CADR ratings.
- Myth: CADR is the only metric that matters. Reality: Noise levels, filter life, and energy efficiency are also important considerations.
- Myth: An air purifier with good CADR will perform the same in any room. Reality: Room layout, ventilation, and ongoing sources of pollution affect real-world performance.
- Myth: All CADR ratings are tested the same way. Reality: Only AHAM-verified ratings follow the standardized testing protocol.
Remember that while CADR provides valuable information, it should be one of several factors in your decision-making process. Consider your specific air quality concerns, noise tolerance, aesthetic preferences, and budget when selecting an air purifier.