According to Kelly Hughes, spokesman for the DoD’s Joint Non-Lethal Weapons Program, the CWC prohibits some temporarily disabling compounds on the basis of whether they activate the trigeminal nerve when people are exposed to it - those that do are classed as riot-control agents (RCA). The nerve conveys sensation from the face, cheeks and jaw, but does not control smell.
“If a particular malodorant is disseminated with a concentration that does not activate the trigeminal nerve, it may not require designation as an RCA under the CWC,” says Hughes.
Stink bombs do not cause injury, but the intense, unfamiliar foul smells affect the amygdala and trigger an unthinking fear reaction that causes the target to flee. This has led to a long history of Pentagon interest in malodorants, but little has come of it (New Scientist, 7 July 2001, p 42).
Now, regardless of whether the loophole is real, the DoD is moving ahead with developing stink bombs. Among them is the US Navy initiative for malodorant grenades, which can be thrown, or fired from a grenade launcher. The aim is to encapsulate the malodorant without leakage and deliver a payload that could clear a 5-metre-square room. Previous efforts have failed because the undisclosed compound involved is highly volatile.