It is also imperative that the vent valve be open for the entire vent step. An open switch on the vent valve is provided for this positive indicator, as well as a vent closed switch. Should the vent open switch be seen as “not made,” or the “vent closed” switch be seen as “made,” or if both switches are seen as both “made,” at any time during the Vent Step, an Uncleared Deviation condition is created.