Tips & Tricks/01.20.22

Air Changes Per Hour: What's Right?

What's the right number of air filtration air changes per hour (ACH)? That depends.

If an IAQ professional is retained for the project, they will calculate the number of air exchanges per hour based on the type of project (mold remediation, dust control, fire restoration, etc.). See how to calculate ACH below.

For dust control purposes, such as a construction project, 2–4 ACH are normally sufficient.

On mold remediation projects, 4 ACH is common, although some indoor environmental professionals, such as industrial hygienists, may suggest 6–12 air exchanges per hour for mold remediation and similar projects.

As a general rule, an air scrubber should achieve a minimum of 6 ACH or one every 10 minutes. If you can increase the ACH, do so.

You can determine the CFM needed to achieve 6 ACH with a simple 2-step formula:

  1. Calculate the room's volume in cubic feet (L x W x H)

    2. Divide the cubic feet by 10 to calculate cubic feet per minute (CFM) needed.

Deploy one or more air scrubbers, based on their CFM. Engineered for optimized air exchange and portability, the HEPA 700 delivers variable airflow up to 700 CFM, so up to 6 ACH (air changes per hour) in 7,000 cu. ft. spaces.

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