How Many Air Changes Per Hour Do You Need?

When people are buying air purifiers, there are often a variety of features and metrics they need to acquaint themselves with to make an informed buying decision. One of the things that can trip people up is the number of air changes per hour a given air purifier can perform. Here’s what you need to know about air changes and how many you need for optimal air quality.


  Why Are Air Changes Important?


Simply put, an air change represents one cycle of all the air in a room being run through the purifier. The more air changes a given unit can perform per hour, the more times the air is being filtered. Air that is purified more frequently is less likely to allow new contaminants to build up, ensuring that air quality stays high.


  Calculating Air Changes Per Hour


The number of air changes per hour a given unit can perform can be easily calculated using the purifier’s flow rate and the volume of the room in question. To do this, multiply the unit’s per-minute flow rate by 60, then divide the result by the total volume of the space it’s being used in.


As an example, let’s take the Amaircare 3000 VOC, which has a maximum flow rate of 225 cubic feet per minute. Multiplied by 60 to account for one hour of runtime, we find that this air purifier can move a maximum of 13,500 cubic feet of air per hour. If used in a room that is 20 feet long and 20 feet wide with 8-foot ceilings (whose volume is 3,200 cubic feet), the Amaircare 3000 can perform approximately 4.2 air changes each hour.


In some cases, air purifier companies make this a process a little easier by stating the number of air changes per hour their units can perform in spaces of a given size. The Blueair Pro XL, for instance, will perform up to 5 air changes each hour in spaces of up to 1,180 square feet. Keep in mind that air purifier coverage ratings assume standard 8-foot ceilings, so what this rating really means is that the Pro XL can perform 5 air changes in spaces with volumes of up to 9,440 cubic feet.


  How Many Air Changes Per Hour Do You Need in Different Rooms?


Now that you can calculate air changes per hour, it’s time to consider how many you really need. While the ideal number for your needs will depend on exactly what contaminants you’re dealing with, most residential spaces do best with 3-8 changes each hour. At these levels, contaminants will be filtered out quickly, leaving your air in the best possible  shape.


For more information about the best number of air changes for each room in your house, we recommend checking out the excellent chart on this web page. As you can see from this chart, optimal air changes are lowest in rooms with minimal contamination, such as bedrooms, and highest in kitchens and laundry rooms where fumes may be wreaking havoc with air quality.


Have questions about which air purifier is right for your home? We’re here to help. Feel free to contact us and we’ll be happy to provide you with answers, information and personalized product recommendations.