To minimize postoperative infections, ultraclean laminar airflow (LAF) units equipped with high-efficiency particulate air filters developed for electronic and aerospace technology have been adapted for ORs. Traditionally, the airflow was either vertical or horizontal and, to function properly, encompassed extra side walls inside the OR. Recently, new airstream technology has provided zoned down-flow units that provide an exponential airflow (ie, resembling an upside-down trumpet mouth). The exponential airflow allows for omission of extra side walls, making them more versatile in clinical use. Each different type of LAF requires knowledge of airstream patterns and how OR team members need to dress and work to prevent contamination of the sterile air and the aseptic areas. This article discusses different LAF systems and related demands on OR clothing and behavior. AORN J 67 (April 1998) 841-851.