In reality, its the opposite.
This unit is used not to kill canaries, but to revive them.
The cylinder attached to the top of the metal box contains life giving oxygen.
They are known as Canary Resuscitators.
If there is carbon monoxide in the air, the canary would show signs of distress.
It would startswaying noticeablyon its perch and eventually fall of it.
The miners would then evacuate the danger area.
In the late 1890s, Haldane began experimenting on small animals like white mice and canaries.
Canaries are especially good at detecting toxins in the air because of their specialized respiratory system.
Animation showing the difference between human and bird respiratory system.
This is important for birds because flying uses a lot of energy.
Also, birds sometimes fly very high up where there is very little oxygen in the air.
The rest is directed into the lungs where oxygen and carbon dioxide switch places.
So birds are continuously breathing oxygen both when they inhale and when they exhale.
This makes them superior at taking oxygen, but also leaves them vulnerable to airborne toxins.
The use of canaries in mines wasoutlawed in Britain in 1986.
At that time, more than 200 canary birds were in duty.
