Tuesday, the work to elect a successor for retired Pope Benedict begins.

Some 115 cardinals will decide who will be the new spiritual leader of the world's 1.2-billion Roman Catholics.

The Cardinals set to elect the next Pope aren't the only ones sworn to secrecy.

For those who come into contact with the conclave, including drivers, caterers, cleaners and those who wait on their tables, mum's the word.

About 90 members of the conclave staff took an oath of secrecy Monday, ahead of Tuesday's conclave.

While the Cardinals go behind closed doors to take part in the secret election, the only sign to the public about a decision will be smoke from a copper chimney, installd over the weekend in the Sistine Chapel.

Black smoke, no Pope.

White smoke, success!

"Regarding the first smoke that we might see the last time it was about eight o'clock, shortly after eight o'clock. It was a long time because there is the prayer, there is the voting, there is the meditation, the voting, so, don't expect anything before eight o'clock," says Vatican spokesman Father Tom Rosica.

Contenders for the position hailo from all over, including Brazil. Nigeria, even the United States, making it the first time Americans have even been mentioned.

The Cardinals are expected to vote Tuesday, but Vatican officials say they don't have to and only smoke will tell.

The longest conclave held since the turn of the 20th Century lasted five days.

If a pope is not elected in the first four days of voting, the Cardinals will pause on the fifth day to pray, talk, and listen to a brief speech given by the Senior Cardinal in the Order of Deacons.