What is The Meaning of CADR?
The acronym CADR means Clean Air Delivery Rate and was established by the Association of Home Appliance Manufacturers (or AHAM). It is a numeric value assigned to an air purifier as an indication of the volume of filtered air delivered by (or from) a portable air cleaner (or purifier) and has been used since the 1980s.
Wikipedia goes on to affirm that this also describes how the unit reduces or removes pollen, tobacco smoke and dust from the air. This acronym, in other words, is used as a standard (as uniform as any other standard) for evaluating the effectiveness of portable air cleaners. This is not the method used for whole house units as they require a different system of measurement for effectiveness.
AHAM believes that, because of the large variety of air purifiers available, a standard such as this one is critical, no matter what type of cleaning technology is used to clean the air. Whether it is HEPA filtration or even an Ionizer type cleaning system, the CADR only refers to the resulting air flow.
How is This CADR Numerical Value Arrived at?
The ANSI/AHAM AC-1 standard is used in a simple to understand way to quantify this value:
1.A testing chamber of 1008 cubic feet is set up and the amount of contaminants in the chamber is verified with electronic equipment.
2. The purifier being tested is activated for a period of 20 minutes. During this time, the level of contaminants is re-evaluated, constantly.
3. The natural rate of decay is used as a comparison to the readings of the final readings of the chamber.
4. At the conclusion of the testing for that particular unit, the CADR number is assigned.
The EPA (United States Environmental Protection Agency) explains the CADR as:
“The CADR is a measure of a portable air cleaner’s delivery of contaminant-free air, expressed in cubic feet per minute. For example, if an air cleaner has a CADR of 250 for dust particles, it may reduce dust particle levels to the same concentration as would be achieved by adding 250 cubic feet of clean air each minute.” – Environmental Protection Agency
According to the AHAM, there are Three CADR Ratings, within which properly operating air cleaners must fall:
Tobacco Smoke: 10 to 450 CADR
Dust: 10 to 400 CADR
Pollen: 25 to 450 CADR
These represent the effectiveness against the three most common indoor air pollution elements. The AHAM recommends what they call a ‘2/3 rule’ when it comes to tobacco smoke which means there should be two thirds of the air, in any room, be replaced each minute.
There is an upper meaningful limit to CAR ratings, however, because of the same sized ‘room’ being used for each test.
How accurate are the CADR ratings and are they useful for Evaluating Air Cleaners?
This standard has been used for more than 30 years and gained the support of the AHAM, and the EPA, the Consumers Union and the Federal Trade Commission. These reputable organizations attest to the validity and repeat-ability of the testing and have all adopted it as an effective method of determining an air purifier’s abilities to clean and purify air. This means that CADR guarantees the effectiveness of a cleaner within certain limits, for anyone who wants to buy one. However, caution should always be practiced.
This means, to anyone wanting to purchase these cleaners, that they can be effective, within certain limits. Caution should always be practiced, however.
What are the practical limits of this system of classification?
One expert, namely Ed Sherbenou, of Air Purifier Power. Com, does state there are valid reasons to refer to CADR ratings when making purchasing decisions. However, he adds that the CADR could mislead people if misunderstood:
- The CADR of a particular model, does not address the actual removal of pollutants, specifically the smaller particles that are some of the most dangerous elements of dirty air (especially to those allergic individuals). These small particles are much more numerous than the larger ones that are often seen in sun rays. Simply identifying the rate of air being produced does not tell you whether this is cleaner than the air going into the unit. The more abundant, larger, particles are often cleaned out of the air much more easily, but the smallest, more dangerous ones are not caught in the filter media.
- The test, illustrated above, does not measure the ability of the air purifier to sift through gases, such as Volatile Organic Compounds that can exude from many components in any average house. The CADR rating numbers, again listed above, represent their abilities in removing particles which are different than gaseous compounds. Most commercially available air purifiers have particular difficulty in dealing with these. The technology needed to remove these contamination elements, does not work for particles and, unfortunately, vice versa.
- This testing dos not assist in telling you how well this unit will do over time. The test, being a fairly short one, does not show how this unit will lose its effectiveness over time, as all things ultimately do. The testing protocol (ANSI/AHAM AC-1) calls for the unit to be run on its highest setting. In normal usage, however, they are not always run on high, depending on the size of room and ambient conditions. Not only that, many people run these on their lowest settings because of the noise occasionally associated the high setting. These lower settings reduce the efficiency of the unit.
So CADR ratings can be used effectively, to a certain extent. Mr. Sherbenou states: “The cheaper the purifier, the more important the AHAM air delivery rate becomes, relative only to other units in its price class.” Comparing apples to apples, so as to speak.
Although the CADR for most air purifiers can be found, many companies do not assign these numbers to their products. However, this should not be an impediment to customer’s rights to understanding their importance to their family’s health and comfort.
CADR is a tool for measuring the effectiveness of an air cleaner for your home. It is, however, not the only tool in your arsenal. Other considerations could be its durability over the long term and its ability to filter out gasses including odors. Proper information, testing and actual operation in your home will help you find the best one for you and your family.