Bell Jar Experiment by Priestley

Joseph Priestley in 1770 performed a series of experiments that revealed the essential role of green plants for the purification of air.
Priestley observed that a candle burning in a closed bell-jar soon gets extinguished. Similarly, a mouse would soon suffocate in a closed space of the bell jar.

Priestley’s experiment confirmed that gaseous exchange was going on
and plants were giving out a gas that supported burning and was essential
for the survival of animals.