The air purge collar is used to keep dust, moisture, airborne particles,and vapors away from the sensing head. Clean, oil free air is recommended. The air purge jacket withstands ambient temperatures up to 356 F (180 C) and limited for use in cooling purposes only. The recommended air flow rate is 30 to 60 l/min (0.5 to 1 cfm). The max. pressure is 5 bar.