No, a gas leak typically smells like rotten eggs or sulfur due to the odorant added to natural gas
Smoking for that generation in Japan was a luxury and a way of being social, so all spaces offices, homes, cafs, restaurants, trains, and theatres were all smoker friendly, needless to say, the governments vested interest in the prosperity of the tobacco industry had something to do with smoking being completely unregulated
However, increase in the mean number of VPCs which was 1.2/h prior to smoking, 2.7/h during hour of smoking and 4.3 in next hour of smoking, did not reach statistical significance (p=0.17)
This was especially true for the five flavored cigarette packages