system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How were mines ventilated before electric pumps and fans were invented?
gpt
There were a few different techniques. Clever designs of ventilation shafts could get the air to move from a slight wind and the heat of the ground. Sometimes they would have a fire burning in the mine with a proper chimney that would draw fresh air into the mine. They did also have bellows and fans to blow air into the mine. These bellows could be powered by humans, donkeys, wind or water.