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Eastman Institute for Oral Health / Research / Covid Safety & Resources / Knowing Your Ventilation Rate

Knowing Your Ventilation Rate

Follow this easy process to calculate the ventilation rate in ACH in your treatment rooms.

What You Will Need

  • A CO2 monitor – can be purchased online or in stores for under $250. We used the Aranet4, but any similar CO2 monitor will work. The CO2 monitor should be able to log the measurement data in one-minute intervals, and allow easy download of the data to a cell phone or computer.
  • Household Baking Soda
  • All-Natural Distilled White Vinegar with 5% Acidity
  • A large container or a basin such as a recycle bin, and measuring cup. We recommend lining the container with a heavy duty garbage bag, because staining may occur.
  • Optional: a small oscillating fan operating on low setting – this helps to make air well circulated in the room.

Step-by-Step Process

  1. Download the corresponding app and connect the CO2 monitor to your cell phone via Bluetooth. Set the CO2 monitor to collect measurement data in one-minute intervals.
  2. Measure the outside CO2 level. The outside CO2 level is between 380ppm and 420ppm in most areas. You can assume it is 400ppm, or you can measure it by leaving the CO2 monitor in an outside area close to the building for 5 minutes. You’ll receive one CO2 value - for every minute. You can use the mean value as the outside CO2 level.
  3. For an average-sized dental treatment room (10 x 12 ft or 120 sq ft), add about 3/5 cup (125 g) baking soda to 64 oz. (1893 ml) of the vinegar in the mixing bowl or basin.
    For larger spaces (>200 sq ft), use one full cup of baking soda (8 oz. or 227 g) with one-gallon (3785 ml) vinegar.
  4. With only one person in the room and the door closed, stir or shake the mixture for two minutes (turn on the oscillating fan at low setting if you have one).
  5. Place the CO2 monitor on the dental chair, remove the mixture, leave the room, and close the door. Wait for two hours.
  6. Download the measurement data on the monitor’s app and send the csv file to your computer.
  7. Find the peak CO2 level (this will be the CO2 value right - after you leave the room) and record the time that corresponds to this level. This is the starting time of the CO2 concentration decay, t0.
  8. Input the peak CO2 level and outside CO2 level into this calculator, you will get the value that is “After removal of 63% CO2”. *
  9. From your measurement data, find the CO2 level that is at or closest to the value “After removal of 63% CO2”, and record the time that corresponds to this level, t1.
    (Insert Chart)
  10. Input the time (minutes) elapsed between t0 and t1 (t1-t0) in the calculator, you will get the ventilation rate measured in air exchange per hour (ACH) for this room.

Calculator Link

* A single air change will remove 63% of airborne contaminants from a defined space. In this case, one air change removes 63% of the CO2 in the dental treatment room.  The time needed to remove 63% of CO2 is therefore equivalent to the time needed to complete one air change in the dental treatment room, which is used to calculate the ACH value.