If your pizza stone has burned items of food on it you should set your oven to 260C and then place the pizza stone in the oven for around an hour.
Leave the stone for an hour and then check the stone.
Grease bubbles should be forming and popping on the surface of the stone.
You should then start the auto-clean cycle when the bubbling has stopped and if the stone is very dirty, it may produce a lot of smoke.
Pieces of food should then burn off and when the cycle has finished, you should wait for the oven to cool down.
After the pizza stone has cooled, you should remove the pizza stone from the oven and wipe it down with a clean cloth.