Chemical and simple asphyxiants are substances which can cause suffocation due to the displacement of oxygen in the air. They work by either reducing oxygen levels in the air, or by increasing the concentration of other gases in the air, such as carbon dioxide. Chemical asphyxiants include gases like carbon monoxide, hydrogen sulfide, and chlorine. Simple asphyxiants can be gases like nitrogen, helium, and argon, and can also be dust particles like flour or pollen. In addition to reducing oxygen levels, some asphyxiants can also be toxic when inhaled. As such, people should be aware of the risks associated with using these substances in confined spaces, and should take appropriate safety precautions when working with them.