blue canary
n.— «As miners once used caged canaries to warn them of poisonous gas underground, the greatest fear of these two streetwise veterans is a “blue canary,” a police officer or emergency worker who unknowingly walks into his or her demise.» —“Homeland Security In St. Louis” by Phillip O’Connor St. Louis Post-Dispatch (Missouri) Mar. 23, 2003. (source: Double-Tongued Dictionary)
Further reading
When a teenager went a week without talking as part of a school project, he noticed a surprising side effect: Instead of rehearsing a response to what other people were saying to him, he was focused on listening — and feeling smarter as a result...
A firefighter named Steve in Newport News, Virginia, wonders why in his line of work, and for some police, certain additional kinds of days off after long unbroken shifts are called Kelly days, Kelly shifts, or Kelly time. The term most likely comes...