The most unusual experience that happened to me was in one of the older high rise office buildings downtown Chicago.  I was called in by one of the major Architectural firms because their main office entrance door was slamming every once in a while. The closer, after I made a minor adjustment, was operating properly.  I returned to my office only to have them call again with the same problem.  This time I contacted Mr. Bill Gore, the engineer and inventor of all the new Norton closers.  I asked him to come to the location with me. He also made a minor adjustment and showed me another trick to control doors.

A day later I again received a call complaining that the door was still slamming.  This time I took Dave Shapiro, my business associate. The door was still working perfectly.  We were standing in the hall in front of the door when Dave excused himself and went into the men's room adjacent to the office.  The men's room door had vents as most public toilets had when the building was constructed.  Both the architect and I were opening and closing the door trying to duplicate the problem. Then I heard the flush of the urinal through the vents in the door just as the office door was closing.

Dave returned. I sent him back to flush the urinals and toilets.  And every time he did, the door slammed. The building had a negative pressure and the flushing caused a positive action through the vents of the men's room door, making the door,

(and others on the same floor I found out later), to slam.

Case closed !