What are the Characters on that Sign?

I have another story from the early days of smoking bans on trains, and my solo and perhaps somewhat silly attempts to be a part of educating the masses.

I was in a soft seat car for the 4 hour journey north from Changchun to Harbin. These cars are arranged with groups of 4 seats, 2 facing each other, with a small doilly topped table in between.  As the train left the station, I was very pleased by the fact that I was the only one sitting in my group of 4 seats.
At the first top, a man got on and sat down directly opposite me.  Shortly after getting underway, he lit a cigarrette. I had noticed that there was a NO SMOKING sign above our seating area (picture of a cigarette with an X through it and some characters), so decided to take an indirect approach.  
"Excuse me," I said.  "I'm learning Chinese, and am trying to figure out what that sign says.  Can you help me?
"It says 'no smoking'," he replied, his hands starting to shake because he certainly knew what was coming next.
"In that case, will you please put out your cigarette."  
He did so then slouched down in the seat.  Of all the the seats in all the cars on all the trains in northeast China, he had to get the seat across from the stupid foreigner waging her own personal anti-smoking campaign. 
I thanked him and returned to reading my book. 
A little while later, the train stopped again, and a man took the other empty seat across from me and promptly got out his cigarettes. Smoker #1 watched with a look of amusement and dread as the man lit up, fully aware of the fate that awaited the poor fellow. 
"Excuse me," I said.  "I'm learning Chinese and am trying to figure out the characters on that sign.  Can you help me?"
"It says 'no smoking'," he replied as the man beside him grimaced. 
"In that case, will you please pull out your cigarette?"
He did so, and the two of them sat there in their defeated misery while I moved on to the next chapter of my book.
The train stopped one more time, and one more time a man joined our little group, taking the seat immediately beside me. Smoker #1 and Smoker #2 just looked at him with pity in their eyes.  As he took out his cigarettes, they, using all the body and eye language they could muster, tried desperately to warn him, but it was no use. 
He lit up. 
I struck.
"Excuse me," I said.  "I'm learning Chinese and am trying to figure out the characters on that sign.  Can you help me." 
Smoker #1 and Smoker #2 stared at the floor.
"It says 'no smoking'," he replied.
Smoker # 1 and Smoker#2 buried their heads in their hands.
"In that case,will you please put out your cigarette?" 
He did so, and for the rest of the journey the three defeated smokers sulked in silence, cursing their bad luck of having been stuck sitting next to me while I enjoyed the smoke-free environment.
When I made the return trip to Changchun a few days later I was feeling rather confident in my ability to handle these renegade smokers. After all, the law was on my side. However, this time the men who sat down around me and started smoking were all train conductors and police — the ones who were supposed to be enforcing the ban.  
It was my turn to be defeated and I was the one left sulking and coughing in a blue haze of smoke.