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What is CADR (CLEAN AIR DELIVERY RATE)?

Air purifiers are devices that clean the air by removing a certain percentage of pollutants from the environment. If we explain the RSP term to be used in our expression here; this is an abbreviation formed from the initials of the words Respirable Suspended Particles and includes the expression of respirable particles in the air. This efficiency is expressed by the amount of 0.3-micron RSP particles that it can remove from the air, measured as a percentage, and the volume value of the air supplied to the environment.

There are 3 sizes of particles measured. They each give an indication of the air purifier’s ability to remove the smaller particles (smoke) up to larger-sized particles (pollen).

Smoke CADR (0.09 – 1 micron)
Dust CADR (0.5 – 3 microns)
Pollen CADR (5 – 11 microns)

There are two factors that influence the CADR rating scale. They are the filter efficiency and the airflow through the filters.

The most realistic indicator to use to compare air purifiers is the clean air exchange rate measure known as CADR (Clean Air Delivery Rate). The CADR criterion includes the net air volume product of the air purifier system and the minimum filtration efficiency based on the 0.3 micron DOP test. To achieve this efficiency, it is said that an air purifier (1680 cubic meters/hour) with the efficiency to remove 95% of 0.3-micron particles from 100 cubic feet (26.6 cubic meters) of air per minute would require a 95% DOP filter.

In summary; If 95% clean air is obtained from 1680 cubic meters/hour of air, 1596 cubic meters of fresh air per hour is obtained. If we remember that this is 100 cubic feet per minute or 26.6 cubic meters/minute of fresh air, 1596 cubic meters / 60 minutes = 26.6 cubic meters/min. Obtained. The same result can be obtained from an air purifier of 190 CFM (3190 cubic meters/hr) and 50% efficiency (based on 0.3 microns).

3190 cubic meters/hour x 0.5 = 1595 cubic meters/hour of the ambient air contains the vapour and absorbency of the surface, and the odour, vapour and gas collection efficiency should be remembered as a function of time. The temperature, humidity and odour factors that affect the event should not be forgotten.

Clean Air Delivery Rate to Room Size

You may be wondering how to convert CADR to practical values, such as your room size. According to AHAM, they recommend taking the CADR rating and multiplying it by 1.55 to get the room size.
This is based on a ceiling height of 8 feet.
For example, a 100 CADR air purifier will clean a 155 square foot room.
Another way is to understand the size of your room and find the correct CADR. Then divide the square footage of the room by 1.55.
Suppose your room has 250 square feet. Divide by 1.55 to get 161.
This means you need an indoor air filter with a CADR of 160 or higher.
AHAM recommends that you use smoke CADR to calculate the square footage of a room.
Since these are the smallest particle sizes they measured, it seems more difficult to get a high score.

What is CADR

CADR particle size

As shown above, there are three CADR numbers.
What you will often see is a CADR rating, in many cases, it is the average of the three ratings.
Although the name is smoke, dust and pollen, this only represents the relative size of the air particles tested.
For example, the range of dust particles can be fine dust smaller than the CADR scale range. The CADR of pollen represents the largest particle in the air.
This represents things such as pet dander, pet hair, dust mites and larger mould spores, pollen, and dust.
Dust CADR is finer pet dander and dust.
If you want to eliminate tobacco smoke, you can say that you want to eliminate smoke particles and odours in tobacco smoke.
Smoke CADR is a misnomer because it only measures particles.
never reflects expectations in terms of removing odours.
Although considering it reflects the smaller sized particles they tested, it is the best number to remove smoke or air pollution.

There are three reasons why air purifier effectiveness is measured by applying the 0.3 micron DOP test.

  1. 0.3-micron particles are particles that can be inhaled and are mostly deposited in the lungs.
  2. K.W. Lee and B.Y.H. Liv announced in April 1980 that the most difficult particles to filter through the air stream are 0.3 microns in size and,
  3. Other test methods other than the DOP test give less realistic results on the retention of respirable particles than the DOP test. Particles larger or smaller than 0.3 microns are easier to filter than those of 0.3 microns. Testing a filter with particles of 0.3-micron size is the best indicator to define filtration adequacy and capability. DOP, known as 0.3-micron particle filtration efficiency testing, is done with 0.3-micron size particles, resulting from the thermal-induced increase, and this test is an excellent indicator of filtration efficiency.
HEPA Filter UK

Air Purifiers to Improve
Indoor Air Quality

Air purifiers provide a significant benefit, along with proper ventilation, to improve air quality and eliminate polluting factors. Today, air-cleaning devices developed with state-of-the-art filtration systems filter viruses, bacteria and microorganisms with HEPA filters and then purify the indoor air with air purification technologies such as UV and Ioniser. Even in devices with the best filtration system, HEPA filters need to be changed every 1-3 months.

These devices filter or neutralize pollutants such as viruses, bacteria, pollen, particles, etc. in the air. They do not affect increasing the amount of oxygen in the air. If possible, the CO2 values ​​in the classrooms should be measured continuously and fresh air intake should be provided to the classrooms.

Sources:
Honeywell Air Cleaners Sales & Applications Information
Air Purifier Ratings Org

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