A method of maintaining sterile surgical instruments sterile. The instruments are placed on a tray located on an upper surface of a sterile gas flow conditioning emitter affixed onto an anatomical surface of a patient adjacent a site of incision. The emitter has upper and lower gas vents from its interior, the upper vent facing and opening across the tray for passing sterile gas across the tray to maintain a sterile field on the tray for the instrument.
