According to KCNC-TV, Denver, teachers and staff were instructed to keep a close eye out for students who appear to be biting on their pens.
Some of the students have been caught using vapor pens, an e-cigarette type device which is like a portable vaporizer. The pens are used to smoke vapor from marijuana and hash oil without any of the strong recognizable smell.
The devices are cheap, retailing for about $25, and they're small and easy to conceal at school. The popularity of vapor pens among teens has triggered the crackdown.