What is the minimum intermittent bathroom exhaust in CFM for residential use?

• A. 25 CFM
• B. 75 CFM
• C. 50 CFM
• D. 100 CFM

Answer: (C)

In residential ventilation, the minimum intermittent exhaust for a bathroom is 50 CFM. This level is chosen to reliably remove humid air and odors when the fan is running, which helps prevent mold growth and keeps the space comfortable after showers or baths. A typical bathroom has a volume that, with 50 CFM, provides about 3 to 5 or more air changes per hour, depending on the exact size, which is generally enough to control moisture. Lower rates, like 25 CFM, may not move enough air to remove humidity quickly, while higher rates (75 or 100 CFM) are often used for larger bathrooms or for faster drying, but the required minimum is 50 CFM.