People who suffer from the sudden, sharp chest pains called angina pectoris usually carry nitroglycerin pills or amyl nitrite for quick, dramatic relief.
If one is exposed to blood agents, amyl nitrite provides an antidote, if administered quickly enough.
When the FDA in 1969 classified amyl nitrite as a prescription drug, many homosexuals switched to isobutyl nitrite, which is not covered by the regulation.