# How a chimney works

How a chimney actually works, and which physical laws apply to the chimney, is explained in detail in this article. Find out why the size ratios in the chimney are so important and why they need to be sized correctly.

### The chimney effect

The chimney effect is the physical principle that ensures that the flue gases are drawn off at the top of the chimney.

For gases of different densities, natural air currents are created. This is called convection. The warm air that comes from the stove, for example, has a lower density than the cold air in the chimney.

#### Convection principle inside the fireplace

According to the principles of convection, this creates a vertical upward flow of air because the less dense warm air tends to rise. It also does this within the chimney - this automatically directs the exhaust gases out through the chimney.

The convection principle is a natural physical principle, which is also clearly visible in the thermals: birds or gliders can be carried upwards, for example, by the warmer air currents in the ambient air.

### Bernoulli effect

The Bernoulli effect is the second important physical law that comes into play by the fireplace. The theory is complex - but in the fireplace it is quite simple: the rising warm air creates a negative pressure in the interior of the fireplace, which pulls up more air.

In this way, the exhaust gases and combustion gases from stoves and heating systems are pulled upwards through the chimney (suction effect).

After the first effect (the chimney effect), which is caused only by upward flowing air sets