Half of all fire deaths in the United States happen at night when most people are asleep, according to the National Fire Protection Agency. You can increase your odds of surviving a house fire by doing one simple thing: Close your bedroom door before you go to sleep.

A shut door keeps smoke and heat out of the room longer, buying you extra seconds or even minutes to plan a way out of the room and out of the house.

In the video below, a test conducted by UL, a global independent safety company, demonstrates the importance of this safety move. Researchers lit a fire in a building with two upstairs bedrooms. They left one bedroom door open and closed the other one. As a fire rages, the bedroom with the open door fills with thick, black smoke. Nearly two minutes later, smoke seeps into the bedroom with the closed door.

This advice may give parents pause — what if you have a baby or young child in the house, and you need to hear her at night? Get a baby monitor, experts say. That way you can still keep an ear out.

Of course, a closed door is no substitute for a smoke detector. Put one inside and outside of every bedroom in your home. Also, make a fire escape plan with your family and practice it twice a year.

Related: Quiz: Are You Prepared for a House Fire?

Angela is a Pulitzer Prize-winning digital editor with more than 15 years of experience delivering news and information to audiences worldwide. Prior to joining SafeBee, she was the features editor for Boston.com at The Boston Globe, overseeing health, travel, entertainment, business and lifestyle coverage. Before moving to features, she was the news and homepage editor, covering stories such as the Boston Marathon bombing, Red Sox World Series victories, presidential elections, a papal inauguration, and more. Her favorite safety tip: Clean your phone! The average cell phone has 18 times more germs than the toilet handle in a men’s restroom.