Photo © James Richard Covington, Jr
I imagine the first vent is the outflow valve?
I imagine the secod valves function is live the manhole cover on the DC8 and prevents presurizing on the ground?
The third I imagine is the over pressure relief valve?
If theses vents are associated with the pressurization system then why are they located on the foward side of the aircraft and not on the rear bottom where they are usually found?