Why does the chimney in a farmhouse automatically exhaust smoke

1. In the absence of wind, the gas inside the chimney is high in temperature and low in density, so it will rise naturally.

2. In a windy condition, the air flow rate outside the chimney is high and the air flow rate inside the chimney is low. High gas flow rate is low pressure, low flow rate is high pressure, so the pressure outside the chimney is lower than the pressure inside the chimney, the chimney gas is "pumped" to the outside by the pressure difference. The higher the wind, the higher the pumping force. This also explains why the farmhouse stove on windy days particularly strong.