Calculate CADR Needed for Target ACH

Though ventilation in dental office spaces could be improved in theory by modifying the HVAC system or opening windows or doors, this is often difficult to realize in practice due to weather or climate conditions. Instead, portable air cleaners (PACs) with HEPA filters could be added to dental treatment rooms to improve the air quality and increase the equivalent clean air ACH through air filtration.

The air cleaning or filtration efficiency of PACs is rated by its Clean Air Delivery Rate (CADR), which is expressed in the volume of filtered clean air delivered by an air cleaner per minute (cubic feet per minute, CFM). The CADR of a specific brand of PAC is measured by the Association of Home Appliance Manufacturers (AHAM) to indicate the PAC’s ability to reduce smoke, dust, and pollen particles between the range of 0.09 to 11 µm in diameters.

The AHAM seal lists three CADR rating numbers - one each for tobacco smoke (0.09 to 1.0µm), pollen (0.5 to 3.0 µm), and dust (0.5 to 11.0 µm). The CADR number indicates the volume of filtered air delivered by an air cleaner. The higher the CADR numbers, the faster the PAC cleans the air. When selecting a PAC for your dental treatment rooms, use the rating for tobacco smoke, which represents the sizes of small dental aerosols that are the most difficult to clean.

If you decide to raise the ventilation rate of your dental treatment rooms to an equivalent of 15 ACH (target ACH), you will first need to know what CADR the PAC must have to deliver the additional number of ACH needed. For example, if you found that your dental treatment room has a current ACH of 2.0, you will need to add 13 additional ACH to reach 15.

  1. Measure the length, width, and height of your dental treatment room.
  2. Input the height, length, and width of the room in this calculator
  3. Input the current Air Change Rate (2.0, for example)
  4. Input the target Air Change Rate (15, as suggested above)
  5. Click the “Calculate” button, the number you get is the CADR needed when purchasing a PAC to place in the dental treatment room.

Room Dimensions

Air Change Rate

Portable Air Cleaner

/* */

Field Descriptions

  • Length: Length of the dental treatment room in feet.
  • Width: Width of the dental treatment room in feet.
  • Height: Height of the dental treatment room in feet.
  • ACHtarget: This is the air change rate need to reach for the room.
  • ACHcurrent: This is the air change rate of the room in current condition. It can be estimated by time needed to remove 63% CO2.
  • CADR: Clean air delivery rate of the portable air cleaner required to raise current air change rate to need.

Questions?  Contact Eastman Institute for Oral Health experts at