Visible crew/equipment: In their first visit to the Vatican Archives, Robert and Vittoria are sitting at the table across from one another. When Vittoria asks Robert "Do you need help with Latin?" the shadow of the boom mic is seen moving on Robert's face. (00:37:45)
Visible crew/equipment: In St. Peters Square at 8:58pm the head of the Saints statue looks like Director Ron Howard. (00:57:25)
Chosen answer: In reality, they would have perished from CO2 poisoning long before the room ran out of breathable oxygen causing them to simply suffocate. Without knowing the exact dimensions of the room it is impossible to give any time more specific than "several hours" for this to happen in a room as big as that one appeared to be.
Phixius ★
I just re-watched the movie, and as Langdon and Vittoria enter the room, it's mentioned to them that the oxygen levels are always kept at a bare minimum to protect the ancient tomes and documents stored there. That helps to answer my own question about why Langdon and the cop were so quickly affected when the power was shut off.
raywest ★