What Is CADR Rating?

What the CADR rating tells you and what it doesn’t.

Air purifiers have become more popular than ever — and it comes as no surprise! These devices provide an easy way to get cleaner air within your home. Individuals dealing with allergies, asthma or other respiratory conditions might see these devices as essential.

But buying the right one can be tricky. One of the main things that air purifiers are rated by is a term called CADR. But what exactly does that mean and how does it affect the efficiency? Is it important to choose one with the highest rating? Let’s find out.

What Is CADR Rating?

CADR stands for Clean Air Delivery Rate. It’s a rating assigned to an air purifier when independently tested by the AHAM (Association of Home Appliance Manufacturers). The AHAM has been hard at work, measuring the CADR of purifiers since the 1980s.

The CADR is basically supposed to be an easy way for consumers to evaluate an air purifier. The rating is only an indication of the volume of clean, filtered air which the specific air purifier will produce.

Is the CADR rating is the same for air purifiers that use different purification methods, such as ionizers or HEPA filters? The answer is yes. CADR ratings are valid regardless of the purification technology used.

The CADR simply is a rating of the end results, not how the specific unit purifies the air.

When looking at the CADR rating, it’s important to note the room size the air purifier was designed for. A unit with a CADR rating of 200 cfm (cubic feet per minute), won’t do as well as an air purifier with a rating of 300 cfm.

It’s safe to say that the air purifier with the highest CADR rating is the most powerful. However, there are a few things one must know before settling for the highest CADR.

Keep In Mind

It’s important to remember that CADR testing is only used on portable air purifiers and not whole-house units. Whole-house air purifiers require a different method.

How to Determine CADR

The air purifier is tested through a process called the ANSI/AHAM AC-1 standard. This process has specific requirements that the air purifier has to meet in order to be certified. The requirements include the following:

  • The air purifier is tested in a room or chamber that measures 1008 cubic feet.
  • Contaminants in that room are measured before the testing to give an accurate result.
  • The air purifier is activated for 20 minutes, while the amount of contaminants are periodically measured.
  • The decrease in contaminants has to be compared to the regular rate of decay.

Once the test is done, the testers will give the air purifier its rating. The CADR rating is measured in cubic feet per minute (cfm). The EPA explains that using a purifier with a CADR of 250, it would be the same as adding 250 cubic feet of clean air per minute.

CADR Rating Categories

When you’re researching a potential air purifier, you’ll likely notice three CADR ratings. This is because each unit has to test its effectiveness against three common indoor air pollutants to achieve the AHAM seal of approval. The three categories you’ll find include tobacco smoke, dust and pollen.

The CADR rating can vary, but one unit will usually have close ratings between the three categories. However, there’s a limit and minimum number for each contaminant category:

  • Dust: 10 to 400 CADR.
  • Pollen: 10 to 450 CADR.
  • Tobacco smoke: 10 to 450 CADR.

Experts will generally recommend air purifiers with a CADR rating above 150. Anything above 350 is highly effective, whereas units with a rating under 100 won’t perform well (1).

How Accurate Are CADR Ratings?

CADR ratings are a good starting point to know whether an air purifier is effective or not. CADR testing has a long history and is recognized by reputable organizations like the EPA, FTC. It’s also trusted by independent organizations like Consumers Union.

Because of the recognition, you can and should trust the CADR rating of an air purifier. If anything, it’s a good starting point when you’re shopping for an air purifier.

CADR Limits and What You Should Know

When looking at the CADR rating of an air purifier, it’s important to know a few points:

  • Small particles aren’t included: The CADR rating tells you the overall performance of the particular unit. However, it won’t tell you its effectiveness against smaller particles. If you suffer from allergies or asthma, the smallest pollutants are likely the most troublesome. Some units are highly effective at removing larger particles — therefore scoring a high rating — but fail to remove the tiniest particles.
  • Gas isn’t measured: You likely noticed that CADR rating only covers three categories, and gases aren’t included. However, gases, such as VOCs, can be very dangerous to the health of you and your family. Gases require a different filtration method than solid particles, such as activated carbon.
  • Air purifiers run on highest setting: When tested, the air purifier will be set on its highest setting. However, most homeowners avoid the highest setting while in the room due to noise levels. This is important to consider since you shouldn’t assume it’s as effective as its CADR rating when on a lower setting.
  • Won’t show wear: Similarly to other appliances, air purifiers will wear overtime — some quicker than others. Because the test is so short (20 minutes), it won’t tell you how or when the unit will decline in its effectiveness.

Experts say that the AHAM’s CADR rating is more important when it comes to cheaper air purifiers. When you’re searching for a unit, you’ll likely notice that not all manufacturers show a CADR rating. Many high-end units manufactured by well-respected companies often choose not to give their products a CADR rating.

CADR Critics and Controversies

Despite being recognized as an accurate way of measuring the performance of air cleaners, the CADR method has received criticism.

In 2003, The Sharper Image sued Consumer Reports’s magazine publisher, Consumer’s Union, based on a bad review. The Sharper Image is the creator of one of the most popular home air purifiers once on the market; the Ionic Breeze (2).

The Ionic Breeze used an ionizer to clean the air, but as Consumer Reports compared it to the traditional HEPA filters, it fell rather short. Consumer Reports found its CADR rating to be very low. To make matters worse, the magazine also found that it actually produced significant amounts of ozone.

Keep In Mind

Ozone might be the protective layer between the sun’s strong UV rays and us, but it can also be harmful when at ground levels (3).

The Takeaway

The Clean Air Delivery Rate (CADR) of an air purifier is an excellent way to tell how a unit will perform. An air purifier is tested for effectiveness against three common air pollutants: pollen, dust and smoke.

However, the CADR rating won’t tell you if a unit removes gases or how well it performs over time. So if you have allergies or asthma, choosing an air purifier with a high CADR rating won’t be enough.

A high CADR rating won’t tell you if the unit removes small particles. So we highly recommend that you choose an air purifier with a True HEPA or medical-grade HEPA filter, as these will remove the smallest pollutants.

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About the Author

Matthew Sullivan

Matthew is a freelance writer with several years of experience in DIY and HVAC. For as long as he can remember, Matthew has always found great pleasure in taking things apart and learning how to put them back together.