What is the recommended ratio of fresh air exchanges to recirculated air per hour in Class A ORs?

a. 5 air exchanges with 1 exchange of outside air
b. 10 air exchanges with 2 exchanges of outside air
c. 15 air exchanges per hour with 3 exchanges of outside air
d. 25 air exchanges with 5 exchanges of outside air

ANS: C
Fifteen air changes per hour (ACH) with three exchanges of outside air (OA) are recommended for Class A operating rooms. Class B and C operating rooms and caesarean delivery suites require twenty ACH with four OA exchanges according to the 2010 AIA Guidelines for Design and Construction of Health Care Facilities.