MADISON, Wis. -- WISC-TV has been reporting this week that smoke alarms fail to wake up most sleeping children.

According to a sleep medicine specialist for Dean/St. Mary's, there are physiological reasons why kids may not respond to loud noises while sleeping.

"You really cannot count on a kid of any young age awakening knowing what to do," said Dr. Kathryn Middleton.

WISC-TV monitored the sleeping patterns of a 9-year-old volunteer at St. Mary's Sleep Lab to show how deeply the typical child sleeps.

"She sleeps pretty soundly," said our volunteer's mom, Vicky Padway, "And she falls asleep quickly."

"Most people have their deep sleep in the beginning portion of the night," said Dr. Middleton, "And it's especially true of children who fall into that sleep very quickly after they fall asleep."

Because WISC-TV's volunteer was hooked up to monitors with wires and electrodes, it took her more than 30 minutes to finally drift off. Another 30 minutes later, she was in deep sleep.

Middleton told WISC-TV, children have more deep sleep than adults, the sleep that's difficult to awaken from.

"A child will have maybe 30 percent, a third of their night, would be deep sleep. Whereas an adult could often be more like 10 percent," said Dr. Middleton.

St. Mary's Sleep Lab Technician Dave Sprecher said kids sleep soundly because they're growing.

"The body releases the most growth hormones than it does the entire day in deep sleep," said Sprecher. "Kids do the majority of their growing at night when they're sleeping."

And studies show that even when children wake during a deep sleep, they are often not alert.

"You wouldn't be surprised if a person would awaken from slow wave sleep or be awakened from slow wave sleep and not know where they were and not know to get out of the smoke," said Dr. Middleton.

Fire officials say you have no more than three minutes to escape a burning home.

Middleton recommended parents adjust their emergency evacuation plans by realizing smoke alarms may not alert their children.

"It's wonderful to have a fire alarm," Middleton said. "But it's more for the adults than it is for the kids."