A Containment Secondary Engineering Control has how many air changes per hour?

• A. 8
• B. 12
• C. 20
• D. 30

Answer: (B)

Air changes per hour show how often the room’s air is refreshed to dilute and remove airborne contaminants and to help maintain the negative pressure that contains them. For a containment secondary engineering control, the standard minimum is 12 air changes per hour, which provides adequate dilution of contaminants while keeping energy use reasonable and meeting common containment guidelines. Fewer changes (like eight) can allow buildup of contaminants, while higher rates (twenty or thirty) are more stringent and used in specific, more demanding setups.