It takes just 30 seconds for a small flame to get out of control and start a fire in your home. Minutes later, thick black smoke has filled your home. If you wake up to a fire, you only have time to escape – flames move too quickly and are too deadly.

The U.S. Fire Association says that toxic gases and smoke kills far more often than actual fire. Fire deaths are on the rise – in 2012, 2,855 people died nationwide from fires but the most recent data from 2015 shows 3,275 people died.

Keeping your smoke detector in good working order is the number one way to protect yourself from injury or death in the home.

Maria Pina with Colorado River Fire Rescue says there’s another trick you can pull to help save you and your family’s lives.

Close your bedroom door.

It’s that simple – and it can be a major difference between life and death. Of course, you should have smoke detectors in every room of your house, but shutting your bedroom door and stave off the fire for an extra 20 – 30 minutes depending.

“We want people to change their smoke detector batteries, that’s the first line of defense,” Pina says. “But I always try to think about simple lifestyle changes that people can change now.”

She talks about a recent fire her department dealt with at a home; the fire raged outside the boy’s room but his door was shut. Pina says he was fine.

“If the door would have been open, the child would have passed away,” she says.

Because it’s those toxic fumes that engulf your home during a blaze. Smoke is extremely bad for anyone who breathes it in and can be a killer, but Pina points to modern items in the home that can kill just as easily.

“Everything is synthetic these days,” she says. “If there’s toxic gases and smoke coming in, it could kill you in one breath – especially if it’s heated.”

She adds that newer homes burn more quickly than older homes, so that’s something to keep in mind. Just taking a couch, for example, the material and the foam inside is toxic. If it’s burning and releasing the fumes from those chemicals into the air – that’s extremely dangerous.

But what about the space UNDER a door?

Pina says sometimes only flames flick under the door, but the smoke stays outside. “That might not happen every time,” she goes on to explain. “But the temperature outside the door could be 600 degrees – the temperature inside might be 100. It’s hot but survivable.”

And that’s the most important thing. It’s why, she says, despite the fact that some children hate sleeping with the door closed, it may just save their life.

Find out more about national fire stats at this link via the U.S. Fire Administration. Also remember to CHECK THOSE BATTERIES! Nothing could save your life more than a working smoke detector.