I wonder whether sprinklers installed 40 years ago are still in working order?  Fire regulations require that fire alarms, standpipes, etc. must be tested once per year.  But I doubt that old sprinklers have ever been tested.  Just think -- how would you test whether a sprinkler is working?  You'd have to turn it on and verify that sufficient water comes out to kill a fire.  You'd need to be sure water is coming out of every sprinkler head.  In every apartment.  Testing would mean every item in every apartment gets sprayed with water including electronics, couches, beds, carpets, books -- everything.  No wonder sprinkler systems never get tested even long after they get installed and get rusty.  Are they reliable decades later?  Nobody knows.