Eli5: how come when you light a barbecue the spark doesn’t ignite all the gas in the pipes?

Question

Eli5: how come when you light a barbecue the spark doesn’t ignite all the gas in the pipes?

In: Physics

Answer 1

For gas to burn it needs to be mixed with the right amount of oxygen (which just comes from the air).

Inside the cylinder and pipes there is no air – only the gas being released – so it cannot burn. When it reaches the nozzle at the end it will start to mix, and can be ignited.