PHILADELPHIA (CBS) — When you go to bed tonight, did you know that there is a preemptive move you can make to prevent a fire from spreading quickly in your home, to help people get out safely?

Highlighting the “Close Before You Doze” campaign, the Philadelphia Fire Department intentionally set a demonstration only home ablaze, by putting a candle to a living room sofa.

“Inside the building the fire creates its own microclimate,” said Fire Commissioner Adam Thiel.

He says it dramatically shows closing all room doors in your house can save lives.

“Essentially, the difference between the closed-door bedroom and the open door bedroom can be about 900-degrees Fahrenheit,” he said.

Director Steve Kerber of the UL Firefighter Safety Research Institute (FSRI), which studies fire behavior and firefighter tactics, says the temperature never exceeded 100-degrees in the closed bedroom.

“So in the test case here, if they’re behind a closed-door, they’re very save-able,” he said. “If their bedroom door is open, chances are, they’re not coming out.”

Its data shows 40-years ago, victims had an average of 17-minutes to escape a burning home.

These days, after a smoke alarm goes off, because of the open layout of modern homes, evolution in interior furnishings and construction materials, the time has dropped to three minutes.