According to Fungal Contamination, what is a realistic starting point for air changes per hour for small areas?

• A. 4 ACH
• B. 8 ACH
• C. 12 ACH
• D. 2 ACH

Answer: (B)

Air changes per hour tell you how many times the air in a room is replaced in an hour, which is a key way to dilute and remove airborne contaminants like fungal spores. For a small area, eight air changes per hour is a practical starting point because it provides meaningful dilution during cleanup and normal use without the extra energy cost and potential noise of much higher rates. Lower rates, such as two or four ACH, often don’t dilute spores quickly enough and can leave contamination lingering. Pushing to twelve ACH can be excessive for a small space, offering diminishing returns on removal relative to the added cost. Start at eight ACH and tailor up or down based on the contamination level, monitoring results, and any additional controls like HEPA filtration or containment you have in place.