Ahead of the conclave to elect the next successor to Saint Peter, Vatican firefighters have installed a smokestack above the Sistine Chapel. It is the smokestack that signals the outcome and will be the focus of all eyes once the conclave begins. After every two rounds of voting in the Sistine Chapel, the cardinals' ballots are burned in a special furnace to announce the results to the outside world.

If black smoke comes out, it symbolically indicates that a pope has not yet been elected, and if white smoke comes out, a new pope has been elected. The ballots are mixed with potassium perchlorate, anthracene (a component of coal tar) and sulfur to produce the black smoke. But if the Pope is elected, the ballots are mixed with potassium chlorate, lactose, and chloroform resin and set ablaze, emitting white smoke.

Since each conclave is held in great secrecy, the first thing the outside world will know about the outcome of the papal election is the smokestack. In the last conclave, held in March 2013, white smoke came out of the chimney during the fifth round of voting. This is how the world learned that the pope had been elected. Believers around the world are waiting for the day when the conclave begins on May 7th and the white smoke will rise from the chimney.