Why you should never run through smoke you didn't throw
Unfortunately for her, it wasn't white smoke; it was o-chlorobenzylidene malononitrile, a potent form of tear gas used to teach basic trainees to trust their chemical masks and other gear. But Campbell wasn't wearing chemical gear; she was running full speed and sucking down air on an obstacle course.
Jennifer Campbell, a U.S. Army basic trainee, cries after getting hit in the face with CS gas. (Go90 No Sh*t There I Was screenshot)
So the young soldier got two lungs full of the agitating gas, forcing violent coughs as her drill sergeants got a good laugh and the other trainees scrambled to get their masks on.
But what doesn't kill you makes you stronger, and Campbell got her own laughs when the winds shifted and the rest of her platoon got hit unprotected, including the drill sergeant who triggered her episode. See how it all went down in the Go90 video embedded at the top.