Chemical warfare agents are poisonous vapors, aerosols, liquids, or solids that have toxic effects on people, animals or plants. They can be released in a number of ways such as by bombs or sprayed from aircraft. Some chemical agents are odorless and tasteless. They can have an immediate effect (such as a few seconds to a few minutes), or a delayed effect (from several hours to several days). Even though chemical agents have the potential to be lethal, they are difficult to deliver in lethal concentrations, particularly in outdoor situations where they tend to dissipate rapidly.