A few cigarettes can set off the smoke alarm.

Look at the sensitivity of the smoke detector. If it is a detector in a place like a general guest room hotel, because guests will also have the need to smoke, will one or two cigarettes trigger the alarm of the detector? But if it is a place like a train or an airplane, the detector will be very sensitive, basically as long as there is smoke, it will trigger the alarm.

A few cigarettes can set off the smoke alarm.

Smoking in the hotel. If you smoke in a small room with closed doors and windows, a small amount of smoking may trigger a smoke alarm, so try to open the windows and smoke heavily in the hotel.

On airplanes and high-speed trains, these are not allowed. Because of the sensitivity of the sensor, if you can't draw one, it will trigger an alarm.