Tear gas and pepper spray are widely used by police and military forces throughout the world to control crowds. Because of the dynamic nature of protests, aid workers may find themselves exposed to riot control agents (if you've never been gassed before, the first time can be very disconcerting). Unfortunately, this topic isn't discussed very much in traditional humanitarian security training and manuals. So to learn more we need to look to other sources, in this case, street medics.
Street medics are independent, trained volunteer medical personnel who support activists during protests. Organized street medic groups
have sprung up in a number of Western, urban locations. One of the groups, known as the Black Cross Health Collective
, has published extensive information on the effects of and treating tear gas and pepper spray. Check it out.