Mysterious gas making ppl pass out?

Im currently in Angola africa and theres been someone goin around to schools spraying something that makes ppl faint.The majority of the victims/students that are fainting are females. They say they felt the class room get cold, pain in the throat, headache, and light headed b4 passing out. What could this chemical be?

it's cyanide heavily diluted with pure carbon dioxide
it's like the oldest trick in the book