blue canary
n.— «The report says the department does not outfit all its vehicles with gas detectors or binoculars, which would enable rescue workers to identify a hazardous material by a placard from a safe distance. Instead, some rescue workers say they would use the “blue canary” system, relying on the reactions of other personnel. “It’s a terrible thing, but if the police officers are falling over next to the scene, then you know not to go near it,” one medic said.» —“Report criticizes ‘hazmat’ training Crews seen ‘woefully’ unprepared” by John Drake Washington Times (District of Columbia) Aug. 28, 2001. (source: Double-Tongued Dictionary)