The invention relates to a method for producing quick lime from limestone in a continuously regenerative shaft furnace, characterised in that, starting from standard conditions of excessive combustion air for operating said furnace, said method comprises a step in which the excessive combustion air is progressively reduced down to the moment when a carbon monoxide content higher than 1000 ppm (in volume) is reached at the connection flue between the tanks. A rise then occurs in the gaseous sulphur oxide content at the flue compared to a furnace operated under standard conditions.