Vatican firefighters were seen on the roof of the Sistine Chapel installing the chimney, a key moment in the preparation for the May 7 conclave.
After every two rounds of voting in the Sistine Chapel, the ballots of the cardinals are burned in a special furnace to indicate the outcome to the outside world.
If no pope is chosen, the ballots are mixed with cartridges containing potassium perchlorate, anthracene (a component of coal tar) and sulphur to produce black smoke.
But if there is a winner, the burning ballots are mixed with potassium chlorate, lactose and chloroform resin to produce the white smoke. (AP)















