Trivia: In the original script the movie was supposed to be set in New York City, but after the September 11 attacks the location was moved to Baltimore.
Trivia: Jacinda Barrett's father was a fire fighter in Brisbane, Australia. She has been quoted as saying that's what drew her to working on this movie.
Answer: I'm not a fire fighter so I do not have a answer based on experience but I assume that when Jack was disoriented it's because there was no light in the building, then when the fire broke through it produced enough light to break through the smoke and make seeing easier for him to escape.
It actually doesn't break through the floor...it's a flashover where everything including the gases in the smoke reach their ignition temperature simultaneously and the room lights off...it's a very serious and dangerous situation to be in as a firefighter...I was in one, luckily we were only 10 feet inside the door.
Steve Kozak