The United States used to deploy this agent in
GB-55 rockets, and we always brought rabbits
with us when we entered the bunkers, and rabbits
were in small cages around the bunkers to detect potential leakers. Other agents are VE, VG and VS. They are generally colorless and odorless liquids which do not evaporate rapidly or freeze at normal temperatures. As they have low volatility, their vapor effect is limioted (good), however the down side is that the duration of lethality is increased.