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Air Purifier CADR-ACH-SQFT Reference

The values in the table below indicate the square foot coverage corresponding to Clear Air Delivery Rate (CADR) and Air Changes Per Hour (ACH). These numbers represent a 100% efficiency system where the CADR is equivalent to Cubic Feet Per Minute (CFM), and assumes nominal 8 ft. ceilings.

Here are a few important notes for you when you are looking at CADR, which is tested and rated for larger air particles such as dust, pollen and smoke only.

  • A high CADR rating won’t tell you if the unit removes small particles (e.g. mold, gas/VOCs, bacteria, viruses and etc.).
  • Some units score high in removing larger particles, but perform poorly in removing smaller particles. In many cases, these smaller particles contribute to your allergies, asthma or other respiratory issues.
  • A high CADR rating won't tell you how well the unit will perform over time. Some will wear quicker over time than others.
  • CADR testing is done with the highest fan speed when noise level is at maximum. In reality, most run their units in lower fan speed with quieter operation. That means the room coverage is less than what is advertised.
  • CADR doesn't really measure how clean the air is coming out of the unit.
  • For example, a 200 CFM unit running at 50% efficiency and a 100 CFM unit running at 100% efficiency both have a CADR of 100. However, the 100% efficiency unit produces cleaner air.
    If you are considering a traditional HEPA/Carbon technology and have the budget, we highly recommend you choose an air purifier with a TRUE HEPA or Medical-Grade HEPA filter.

      Now for some calculations. Assume the following as an example:

      ACH = 2, CADR = 400

      Per the table, the square footage = 1500 (assuming 8 ft. ceiling height)

      CADR = [(ACH x L x W x H) / 60] CFM * Efficiency

      Doing the math we have:

      400 = (2 * 1500 * 8) / 60

      CADR ACH1
      SqFt
      ACH2
      SqFt
      ACH3
      SqFt
      ACH4
      SqFt
      100 750 375 250 188
      150 1125 563 375 250
      200 1500 750 500 375
      250 1875 938 625 469
      300 2250 1125 750 563
      350 2625 1313 875 656
      400 3000 1500 1000 750
      450 3375 1688 1125 844
      500 3750 1876 1250 938

      Read More In our Blog on Air Purifier Size