For a two-car residential garage, what is the maximum ventilation rate allowed?

• A. 150 CFM
• B. 200 CFM
• C. 250 CFM
• D. 300 CFM

Answer: (B)

Understanding ventilation for an attached garage centers on providing enough air exchange to dilute vehicle fumes while staying within code limits. For a two-car residential garage, the maximum allowed ventilation rate is 200 CFM. This level provides roughly 4–6 air changes per hour for typical garage volumes, offering effective dilution of gasoline vapors and carbon monoxide without wasting energy or creating excessive pressure differences that could affect the house. A shorter, smaller rate like 150 CFM might not reliably remove fumes, while larger rates such as 250 or 300 CFM would exceed the code’s maximum for this garage size and could lead to unnecessary energy use or unintended pressurization issues.