When you walk into clouds of poisonous gas for a living, it helps to have a sense of humor–even a morbid one. That&#039s why fire department hazardous-materials specialists often call their police colleagues “blue canaries.” It&#039s a reference to the songbirds that old-time miners took with them underground as living–or dying–indicators of bad air in the shafts. The joke goes like this: “There&#039s a policeman down there, he doesn&#039t look like he&#039s doing too well, I guess that&#039s not a safe area,” explained John Eversole, chief of special functions for the Chicago Fire Department. Full Story