How many air changes per hour are necessary in an unoccupied laboratory?

An unoccupied laboratory typically requires a minimum of four air changes per hour to ensure adequate ventilation. This level of air exchange is critical for maintaining good indoor air quality by diluting and removing airborne contaminants that may have accumulated due to ongoing experiments, even when no personnel are present.

The process of achieving these air changes helps in managing heat load, preventing the build-up of potentially hazardous gases or vapors, and maintaining an overall safe laboratory environment. While some laboratories may have specific requirements that necessitate more frequent air exchanges, four changes per hour is considered a standard baseline for ensuring safety.