Clean Air Delivery Rate (CADR) measures the amount of clean air produced by your Air Cleaner as determined by AHAM. (AHAM stands for the Association of Home Appliance Manufacturers.)

CADR ratings can be a fair guide on the ability of any air purifier to deal with air pollutants. There are always three numbers with regard to CADR: for pollen, for dust, and for smoke.

The tobacco smoke particles range from 0.1 to 0.5 micron. The dust particles range in size from roughly 0.5 to 2.5 micron. The pollen particle sizes range from 5 to 10 microns. Given the average sizes, you might notice that usually the CADR number for tobacco smoke is smaller, as it is more difficult for some units to deal with this type of pollutants.

If dust in your house is a bigger issue than pollen or smoke, you will naturally have to look for a unit with a higher CADR for dust.

CADR of a given air purifier is a number that comes from independent AHAM measurements. One important distinction is that CADR is never assigned to whole-house air purifiers, only to portable units. Whole house units are measured differently.

How is CADR Measured?

Participation in the AHAM measurements is voluntary for all manufacturers of room air purifiers. Here is a simplified description of the test being performed:

  • There is a 1008 cubic feet testing chamber, which the air purifier is placed in.
  • The presence of contaminants in the air is determined prior to activating the machine.
  • The purifier is turned on for 15 minutes.
  • The reduction of contaminants in the room is measured.

The final number (in cubic feet per minute) is a measure of the ability of the air purifier to deliver air free of contaminants. If the CADR is say 150 for dust particles, it means the unit can reduce dust contaminants equivalent to providing 150 cubit feet of clean air per minute.

What is the Highest CADR Rating?

As the test room is always the same, the lower and upper limits to meaningful CADR are the following:

  1. For Tobacco Smoke: from 10 to 450
  2. For Dust: from 10 to 400
  3. For Pollen: from 25 to 450

AHAM SEAL

The 3 CADR numbers are usually found on the AHAM seal on the back of your air purifier’s box. The higher the numbers, the better the air filtering.

It can be argued whether or not CADR provides the best possible system for ranking air purifiers. In the second part of this article we are going to discuss some of the flaws of this system. For now, let’s see how it works.

In principle, the higher the CADR the larger the space that can be cleaned with the same efficiency. The formula is:

CADR x 1.5 equals the room size (in square feet)

Note: the room size is always computed based on the CADR for tobacco smoke.

Why is CADR Invented in the First Place?

Air purifiers are often advertised giving the room size they are recommended for. Various manufacturers may give various room sizes their cleaners can handle, so it might be difficult to compare between them. However, once you know the corresponding CADRs, it is much easier to make your comparison.

Example How to Select the Right CADR Rating?

The CADR rating is actually based on providing clean air to the room (the size of which is determined from the formula above) 5 or 6 times per hour. Let’s see an example:

Let’s suppose an air purifier has a CADR rating of 100. We multiply that number by 1.5, which gives us 150 sq. ft. of room size. So the unit will provide five to six complete air changes for a room of 150 square feet per hour.

You can turn this formula around if it is easier for you to do the math. Say, your room is 15 ft times 10 ft = 150 square feet. For CADR you want at least 23 of your room size, which is 100. You can always use a machine with higher CADR, say 200, as it will clean your room more efficiently. The ceilings height also counts. This calculation won’t be exact for ceilings higher than 8 feet.

Now, for medical applications, high CADR ratings may not mean anything. It is also important to know that CADR is computed for the highest fan speed of the unit in question. With lower fan settings, the efficiency is of course reduced.

Model

CADR dust

CADR pollen

CADR tobacco

Room size

Whirlpool Whispure Air Purifier, AP51030K

325

401

315

472

GermGuardian AC4825

100+

100+

100+

150

Holmes Desktop Air Purifier, HAP242-NUC

70

70

70

105

Honeywell HPA300

320

300

300

450

Honeywell 50250-S True HEPA Air Purifier

250

250

250

375

Honeywell HFD-120-Q QuietClean Tower

100

132

110

165

Winix 5300-2 Air Purifier

243

246

232

348

Honeywell HPA060 True HEPA

62

75

48

72

Coway AP-1512HH Mighty Air Purifier

246

240

233

350

Blueair Classic 505 HEPASilent

400

450

450

675

Whirlpool AP51030PRO

336

350

328

492

Whirlpool Whispure Tower APT40010R

136

150

123

185

Winix hr1000

264

301

258

387

Coway Ap-0512NH

110

110

110

165

Blueair Pro L HepasilentĀ® Air Purifier

>400

>450

>450

>675

IQAir HealthPro Plus

>400

>450

>450

>675


Source:

http://www.ahamdir.com/aham_cm/site/pages/index.html?code=r.rac.AboutThisProgram

http://www.air-purifier-power.com/iq-air-purifier.html

Important notes:

The Limitations of CADR

If you have a medical condition the CADR won’t mean much because it doesn’t reflect the air purifier’s power to capture the smallest particles. And sometimes, the most dangerous pollutants are the smallest particles.

In fact, CADR reflects just about 10% of common airborn contaminants. The CADR test is not designed to measure the removal of ultrafine particles, which are about 90% of all air pollutants.

CADR says nothing of the ability of the air purifier to eliminate the volatile organic compounds, which are gaseous in nature.

As we have seen, the test is done for 20 minutes only. The manufacturers (at least in principle) can manipulate this test by designing their machines to be especially effective at the beginning of operation. It may be very bad if the manufacturer sacrifices long-term performance for initial short-term accomplishment.

Some purifiers may indeed lose their efficiency quickly over time.

If you use your machine on the lower settings to reduce noise, the effectiveness of your unit will be reduced too.

The Bottom Line

Should you use the CADR ratings when you purchase your new Air Purifier?

Sure.

But be aware of its limitations. It will give you an estimate of the overall performance of the machine. But if you want cleaning standards that go beyond the needs of the average customers, you should also look at additional parameters. Especially if you have to deal with sensitivity to special pollutants or allergens.

Image source: https://en.wikipedia.org/wiki/Clean_Air_Delivery_Rate