Answer :
Poisonous Gas is used to kill the enemies. This gas could not harm the people who release it as long as they wear gas masks.
This chemical warfare used today is poisaonis gas. This gas is spreaded over countries or were ever they want to, but they have to water a mask otherwise they wii die to. The gas makes your body not work and you die and now its easier cleaning. Also it won't harm any buildings just the living things. I hoped I helped.