|A no smoking zone|
Evidently all this was too much for one fairly young traveller on our train. I happened to be moving about the train at the very moment that the train crew confronted him with the information that a remotely-monitored smoke detector had gone off in the toilet from which he had just emerged.
His denials didn't carry much weight as the crew (and I) could readily smell that he'd just had a cigarette.
He was escorted to the train manager's office, so I don't know what happened. However, a few minutes later, a "final reminder" announcement was made that anyone caught smoking on the train would be fined and/or off-loaded at the next station. Being off-loaded? An option on the train, but wouldn't work so well for an airline!