Is CADR the Same as CFM?

You’ve probably come across terms like “CADR” and “CFM” when going to buy a purifier. In most cases, you are advised to choose a purifier with a “good CADR”  or enough “CFM.” However, these abbreviations can be confusing, and sometimes, you might use them interchangeably.

CADR has a different meaning from CFM. However, these two terms work hand in hand to determine the efficiency of an air purifier. Though different, you can obtain a CADR rating from a given CFM.

Are these abbreviations a little too much? Don’t worry, as you’re about to get a better understanding of these terms. However, if you have no idea what each abbreviation means, keep reading to learn more. 

What Is CADR?

CADR stands for Clean Air Delivery Rate. This measurement is an invention of the Association of Home Appliance Manufacturers.  The association devised this term for easy quantification of the efficiency of home appliances, including air purifiers. 

To attain a score for an air cleaner, the association tests how well it can remove smoke, pollen, and dust. These substances are all harmful but vary in size, with smaller particles being more dangerous.

For instance, since pollen is large (5-11 microns), it can only cause allergies and trigger asthma. On the other hand, smoke particles are smaller (0.09 – 1 micron) and can get past the body defenses. As a result, they cause more harmful and long term effects.

The testing usually depends on how well the filter can purify the air and the airflow rate through the filters. The latter determines how quick the device can clean small or wide spaces. 

After each device is duly tested, the association scores it based on its performance. The higher the rating, the more functional the device. Therefore, CADR is one of the things to look out for when purchasing an air purifying machine. 

However, AHAM CADR is a voluntary exercise, so not all purifiers have this score. This doesn’t mean that other devices are below the mark; it only means they haven’t been tested and verified by a third party.

Benefits of CADR

The CADR rating benefits consumers by comparing air purifiers’ coverage and filter efficiency. It’s also a means to avoid being duped by the sweet messages of marketing. Once you find this rating, you can decide if the device suits your space or not.

A CADR is simply the multiplication of the device’s efficiency and cubic feet per minute. Therefore, if the device has 300 CFM and a 100% efficiency, the CADR is 300. In the same vein, if it has a 300 CFM and a 50% efficiency, the CADR is 150.

While this test is valid, it doesn’t assure individuals that the device is perfect. For example, the rating won’t tell you if it emits ozone, has low noise levels, or has unique features. Therefore, it’s best to seek out other characteristics of a purifying device, even if it has a high CADR.

Is a Higher CADR Better than a Lower Rating?

Technically, a higher CADR means that the machine is more efficient. So, yes, a higher CADR is better than a lower rating.

For a device to have a better CADR rating, it must have gone through several testing. This measures how fast the air purifier can erase particles of different sizes from the air. It also measures how far the device can circulate clean air in several spaces. 

What Is a CADR Scale?

The rating of a device begins from zero and can go as high as 450. However, the highest CADR varies for different particles.

Below is the CADR scale for the three particles AHAM uses to measure efficiency:

  • Smoke ( 0.09 – 1 micron): 0-400
  • Dust (0.5 – 3 microns): 0-450
  • Pollen (5 – 11 microns): 0-450

When you get a device, you’ll find these three ratings in this form a/b/c. So, for instance, if you see a reading of 200/250/125, the first is for smoke, the second represents dust, and the last, pollen. 

How Is the CADR Device Tested?

AHAM follows a straightforward procedure to test air purifiers. First, the testers place the device in a room measuring 1008 cubic feet. Such wideness usually contains several particles ranging from dust to smoke.

The device is placed in the same room and left to run for at least 25 minutes. Once this is done, the people measure the level of three contaminants – smoke, dust, and pollen. Afterwards, they give a CADR based on the air cleaner’s performance. 

What Does CFM Mean for Air Purifiers?

CFM is an abbreviation that represents Cubic feet per minute. The term describes the flow of gas, liquid or air in and out of a room. 

1 CFM equals 0.47 litres per second; thus, the higher the coefficient, the higher the gas amount entering the space. In the case of air purifiers, the higher the value, the wider the area it can clean. 

The CFM is essential in determining the size of an air-cleaning device suitable for your space. If you get a device with a low CFM for ample space, there’ll be less functionality. Such devices will also have to work twice as hard, damaging the motor quickly.

How to Calculate CFM

CFM equals length x width x height multiplied by (Air Changes per Hour) / 60 minutes.

Calculating the CFM of any space is a straightforward process, provided you are the formula. First, you must know the specified space’s length, width, and height (all in feet). 

You must also know the number of air changes the room needs every hour. Hourly air changes are dependent on how the space is used and the quality of the indoor air.

Most rooms, including living and workspaces, require six air changes hourly due to the low level of indoor air pollution. On the other hand, a large kitchen/dining area will require more air changes than a small bedroom or guest room.

Other spaces like conference rooms, dining halls, and similar spaces typically require eight air changes per hour. Furthermore, areas with higher pollution levels, like designated smoking areas, casinos, and bingo halls, need around 12 air changes hourly.

Is CADR the Same as CFM?

As mentioned earlier, both are distinct, but they work in synchronization to determine a purifier’s competence. First, CADR means Clean Air Delivery Rate while CFM means Cubic Feet per minute.

CADR tells you how the device cleans air volume in every cubic foot. In other words, you can’t calculate the CADR without using the CFM. 

On the other hand, the CFM contains several particles, which determine how fast the purifier can clean. The more polluted the air, the less speed it will take to clean a space.  

How Do You Convert CADR to CFM?

Converting from CADR to CFM is not as straightforward as reverse calculation. In this scenario, you have to divide the rating by efficiency and multiply it by 100. 

For instance, if a device had a CADR of 225 and an efficiency of 75%, the CFM will be 300. 

How did this answer come about? Simple, follow the formula like this:

(225/75) x 100 = 300 

Other Factors to Look out for in a Purifier

During the test, the device is run at its maximum speed. This means that such a rating only tells you how functional a device is when running at its best. 

If you reduce the speed of the fans, the CADR reduces with it. In other words, they won’t be as effective as they should.

AHAM ensures that the purifier has a clean, new filter. Newer filters function better than older ones; therefore, this test doesn’t cover how the device functions when old.

Therefore, don’t be blinded by a high CADR. It might have a filter that’ll only last briefly compared to devices with lower rates.

The best filters are the larger ones as they have better filtering media. In other words, they can remove more particles from the air and last much longer. Conversely, devices with a thin filter have a shorter lifespan regardless of the rating.

The CADR doesn’t also note the noise of the device. If you’re expecting to buy a noiseless air purifier, ensure that noiselessness is part of its feature. 

It’s important to note that a CADR is not a safety test. Thus, the rating wouldn’t tell you how safe the device is for your space. Don’t expect to know things like how much ozone it emits by just reading the CADR.

Frequently Asked Questions

Are There Limitations for CADR?

Yes, CADR has a few limitations. First, the air purifying device focuses on particles rather than gases. The rating is also based on the fan’s highest speed, so the device might not be 100% functional at a lower speed.

Why Is CADR Important?

CADR is vital if you’re concerned about an air cleaner’s performance. It indicates whether the air purifier is powerful enough to clean your living space effectively. Despite this, an air purifier will be ineffective at cleaning your room without sufficient airflow.

How Accurate and Useful Are CADR Ratings?

The CADR rating is the most accurate method for comparing the performance of different air purifiers. Essentially, it provides a numerical value indicating the amount of clean air produced at the highest fan speed.