Before disconnecting the main airline that powers the unit this line must be bled. There is a purge valve that needs to be opened, this purge valve will drain the main air hose pressure and the vacuum system, you must shut off the main air from the source or by turning the vacuum on with main air shut off. Do not remove any lines or clamps unless you are absolutely sure that there is no pressure in lines or hoses.
IT IS IMPORTANT THAT ALL LINES, HOSES AND VESSELS CONTAIN ZERO AIR PRESSURE BEFORE REMOVAL. COMPRESSED AIR MAY CAUSE SEVERE INJURY OR DEATH!