CADR - Assessment standard for air purification devices : Clean Air Delivery Rate

Clean Air Delivery Rate Definition

The Clean Air Delivery Rate is considered the rating standard for air purifiers. Developed by the Association of Home Appliance Manufacturers (AHAM), it is used to evaluate the efficiency and compare the filter performance of air purifiers. Three different types of particles are tested: smoke, dust, and pollen. But how exactly does such a test work? How does the determined value help us to evaluate the filter efficiency? And is an evaluation based on the Clean Air Delivery Rate sufficient to make the right choice of air purifier?

air purifiers and air filter

Clean Air Delivery Rate Calculation and Test Procedure

The test can only be carried out in compliance with the precisely defined test environment and requirements. The room must be 28.5m³ in size and also closed. While the floor consists of a smooth surface, the walls are painted with washable paint. A fan is used to distribute the particles in the test environment. In addition, the room is thoroughly cleaned beforehand and freed from the normal particles. The size of the test particles is also defined as follows:

  • Smoke: Ø 0.09µm - 1.0µm
  • Dust: Ø 0.5µm - 3.0µm
  • Pollen: Ø 5.0µm - 11.0µm

A certain amount of the particles is put into the room. Then wait for one minute to allow the particles to disperse in the room. At one-minute intervals, testing continues for 20 seconds. The test for dust particles and smoke is continued for 20 minutes, whereas the test for pollen is stopped after ten minutes due to the large particle size.

How are the results to be evaluated?

To evaluate the performance of the air purifier and its air filters based on the results, the basic rule is as follows: a low value indicates low performance and the higher the value, the better the efficiency of the air purifier. Due to the statistical accuracy, limits have been defined for the measurability. Thus, the standard only applies to air purifiers with a maximum CADR rating of:

  • Dust particles: 10 - 400 cfm
  • Smoke: 10 - 450 cfm
  • Pollen: 25 - 450 cfm
    dust, pollen and smoke

    What is important to consider?

    Imagine two air purifiers with different CADR values. Then the air purifier with the higher CADR value must definitely be the better one, it's obvious!

    Unfortunately, it is not that simple. It is true that the Clean Air Delivery Rate should definitely be used as a comparative value and first point of reference. However, several aspects of the Clean Air Delivery Rate calculation remain unnoticed. Under the point "Test procedure" we have already dealt with the sizes of the test particles. The smallest defined particle size is 0.09µm. This means that smaller particles are disregarded, which includes viruses or ultra-fine dust particles, for example. Nor does the value make any statement about whether and how efficiently odours are removed by the air purifier. It should also be noted that the test always runs at the highest level of the air purifier. In practice, however, this is not always the case.

    Volume, filter medium and filter class should always be used as further points of comparison in addition to the CADR value. In order to be able to filter even the smallest particles, such as viruses or ultra-fine dust, a HEPA air filter is required for your filter system. Our team will be happy to advise you on this.


    HEPA filter

    For the purpose of comparing different air purifiers, the Clean Air Delivery Rate should be used in any case. However, due to the smallest particles and odours, which are not considered in the test, it makes sense to look at other factors as well. Pay attention to the volume, but above all to the filter class.

    Our filter solutions for your air purifier

    EMW offers you a range of (H)EPA air filters for your existing filter system of mobile room air systems, air cleaners and HVAC systems. We can also offer you customised (H)EPA filter solutions that are optimally tailored to the specific needs of your systems. Our team will be happy to advise you.