Health care ventilation standard: Air changes per hour or CFM/patient?

Ventilation is used throughout the health care setting to maintain good indoor air quality, control contamination concentrations, and control nosocomial infection. Many health care-related ventilation standards are based on air changes per hour (ACH) or the volume of air flowing into a space in one hour divided by the volume of space. A ventilation standard based on cubic feet per minute (cfm) per person is, however, likely to be more representative of expected contamination levels within a space than an ACH standard. With the CFM/person standard, the contamination sources are likely to be related to the infectious patient themselves, or to patients, their visitors, and activities; while room volume is unlikely to be related to contamination sources.