The purpose of the door at the west (N. Adams) end of the Hoosac was to prevent snow from blowing into the tunnel, I have always assumed that this was the reason for doors on those other tunnels which had them. The only tunnels that I know of with doors are all located in heavy snow country. I don't understand how doors would aid in exhausting smoke/fumes from a tunnel. It seems to me they would have the opposite effect and inhibit ventilation.
Mark
