elementary school classroom is recommended to be a minimum 900 square feet (2). Let’s look at an example of this calculation in action.įor this example, we’ll be calculating how many air changes per hour a premium air purifier can deliver in a classroom.Īn average U.S. Related video: What Size Air Cleaning Unit For Your Office? with Camfil’s Matthew Crouch ACH Example Calculation This number is your air changes per hour, or ACH. You now have a number telling you how many times per hour the device moves the total volume of the room. Divide the number you get by the room’s volume in cubic feet.This number will tell you how many cubic feet of air your device moves per hour. ROOM VOLUME – Secondly, you will need to find the volume of the room in cubic feet, which is calculated by finding the height, length, and width of the room in feet and multiplying these numbers together.įrom there, the calculation to find air changes per hour is simple: To calculate air changes per hour, you will need to find two numbers.ĬFM – First, the volume of air in CFM (cubic feet per minute) currently delivered to the room in question by the building’s air handling unit or when evaluating an air purifier, the CFM of the unit with the air filters installed. What Is the Formula for Calculating Air Changes per Hour? Polluted air also leads to moodiness and decreased productivity for employees and reduced learning for students in school.Īdditionally, the EPA asserts that increasing ventilation is an important strategy for decreasing the spread of COVID-19 in public spaces (2). Respiratory diseases, heart disease, and cancer.Irritation of the eyes, nose, and throat.According to the EPA (1), negative health effects of poor indoor air quality include: Improper ventilation can lead to a buildup of pollutants in indoor spaces, which is detrimental to the health of building inhabitants. Ventilation is important for the indoor air quality (IAQ) inside a building. Additionally, if you have chosen to implement air purifiers to improve air quality and lower the risk of COVID-19, ACH will help you determine which devices are appropriate for your application, as well as how many you need. It is also sometimes referred to as “air change rate” or “air exchange rate.” Why Do You Need to Calculate ACH?Īir changes per hour are important in determining if a space is getting adequate ventilation.
What Does Air Changes Per Hour (ACH) Mean in Air Filtration?Īir changes per hour, which is often abbreviated as ACH, is a calculation of how many times per hour the entire volume of air in a given space is replaced with supply and/or recirculated air.
BREATHING ZONE OUTDOOR AIRFLOW CALCULATION HOW TO
In this article, air filtration experts from Camfil explain the importance of air ventilation within a room and how to calculate air changes per hour (ACH).
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