Tear gas, usually in the form of CS or CN.

CS gas or tear gas, not to be confused with CN also called Mace.

Cyanide is CN-1.

Tear gas is actually not a gas, but a vapor. Most tear gas was based on CN- (Phenacyl chloride). Newer riot control gasses are based on CS (2-chlorobenzalmalononitrile)- but are still a vapor and not a gas.

The 12 pairs of nerves that exit the brain are the cranial nerves. (CN I) Olfactory, (CNII) Optic, (CN III) Oculomotor, (CN IV) Trochlear, (CN V) Trigeminal, (CN VI) Abducent, (CN VII) Facial, (CN VIII) Vestibulocochlear, (CN IX) Trigeminal, (CN X) Vagus, (CN XI) Hypoglossal, (CN XII) Hypoglossal Nerves