Unpleasant odors

By now I have traveled enough on trains to not have noticed the motley of smells that sometimes engulf the coach cars. A number of passengers never fail to bring food on board, since it is much cheaper than the food from the dinning car. While this economical decision makes perfect sense, and I would strongly encourage passengers to bring their food, I would expect people would be more conscientious of the smell of their food. There is no need to bring a tuna sandwich, and if you do, then there really exists no reason to eat it in the coach cars instead of the lounge car or observatory...