Canary in the Coal Mine

In the nineteenth and early twentieth centuries, canaries were used in coal mines as an early warning system for detecting carbon monoxide. These small birds, highly sensitive to the gas, would show signs of distress or die from exposure before the levels became dangerous for humans, giving miners crucial extra moments to escape from hazardous conditions. By 1986, domestic canaries and finches were replaced by electronic carbon monoxide sensors, which offer a more accurate and humane method for detecting poisonous gases.

Article "Canaries in the Coal Mine", by Amelie Bonney, Gale Ambassador at the University of Oxford, is a great read if you are looking to find out more on canaries used in mines. The article can be found on The Gale Review blog.