The inside of mines can be very dangerous. In the early days miners could die not only from a poorly made cave collapsing, but also from toxic gases found deep in the ground, or even from a lack of oxygen in the air down in the mine. The especially scary part was that the miners couldn’t immediately tell that the air they were breathing was dangerous—it wouldn’t smell or look weird, so they would just keep on working. Only if a few of the miners died would anyone realize that there was carbon monoxide in the air or that there wasn’t enough oxygen. So as a safety measure, miners started bringing canaries with them down into the mine. Canaries are small, so they’re easy to carry. They’re also constantly inhaling, so if there was anything dangerous in the air, a canary would pass out pretty quickly. This would be a sign to the miners that they should evacuate immediately. Today, we have better technology to test the quality of air, so thankfully, canaries are no longer used. But for the miners in the early nineteen hundreds, when there were no other options, they were a lifesaver!