My wife and I traveled on a RO-RO Passenger ferry. On entering our cabin I noticed that a plastic cup had been jammed over the Smoke Detector. I reported this to a person at reception who politely said she would report the matter. I was not satisfied my report would get to the Master.
Later on, after sailing I happened to see the Chief Officer in an alleyway, so I mentioned the matter to him. He was very concerned and took me to the Bridge to see the Captain who was very grateful for the information. Listening to me on the bridge was a junior Deck Officer, who in my opinion unwisely, volunteered the information that some passengers who smoked routinely did this to stop the smoke alarms being set off!