(WVLT) -- If you have the kind of smoke detector found in most homes, it may not go off if there's a fire in your home tonight.
Our sister station WTVF investigated and discovered the most common type has an alarming rate of failure.
Jennifer Kraus has the details.
"Being killed by smoke is a horrible way to go," said Mike Turner, a representative for the Nashville Metro Fire Department.
If your house catches on fire in the middle of the night, you want a smoke detector that wakes you up at the first sign of smoke.
"Smoke is what kills people, it's rarely that someone gets burned up," said Turner.
But, the kind of smoke detector found in most homes often has trouble detecting the type of smoke that kills.
"If the public was aware of it, it could save hundreds of lives every year," said Deputy Chief Jay Fleming, with the Boston, Tennessee Fire Department.
Chief Fleming has spent years studying smoke detectors.
So, with his help, we put them to the test.
We tested three types of smoke detectors: an Ionization Detector, the cheapest and most common type people have in their homes, a Photoelectric Detector, which is a few dollars more, and a Dual, which is a combination of an Ionization and Photoelectric Detector.
For the test, we invited firefighters from the state and from the Nashville Metro Fire Department, including State Representative Mike Turner to the Tennessee Fire Academy in Bedford County.
"It's going to be interesting," said firefighter Danny Hunt.
Even these firefighters were skeptical that there would be much of a difference between when the detectors would sound.
"I'm going to say 20-25 seconds," said Turner.
"I think maybe a minute tops," said firefighter Jeff Huddleston.
We had six cameras ready to capture every angle.
"What we're trying to do is simulate a cigarette in a couch," said Chief Jay Fleming.
Chief Fleming sticks a hot soldering iron under the cushion.
"This is actually a very common type fire in the U.S. It's a slow-burning fire that creates a lot of smoke, just like fires caused by space heaters and electrical fires," he said. "Now we just have to wait."
About five minutes later we see the first curl of smoke and we start our timer.
"As you can see, the amount of smoke given off is gradually, very slowly increasing," said Chief Fleming.
After about a minute and a half, the room is still basically clear and breathing without a mask is easy.
But as the time reaches four and a half minutes, it gets tougher to breath.
As the room starts to get visibly smokey, one of the detectors goes off.
The Photoelectric Detector sounded at about eight minutes and 15 seconds after smoke was visible.
In a real fire, firefighters say at that point, you would have no trouble getting out alive.
But, the other two detectors are silent, while smoke is filling the small room.
At about ten minutes and 15 seconds, the Dual Detector goes off.
But still, the Ionization Detector, the kind found in most homes, has not sounded.
"I'm surprised it hadn't gone off yet," said Mike Turner.
Now there's so much smoke in the room, Chief Fleming, a veteran firefighter, needs his breathing mask.
"I think people are surprised at how much smoke you can get without having any flames," said Fleming.
And still, the Ionization Smoke Detector has not gone off.
"I'm not saying there isn't a single person in this country who can't escape through this kind of smoke, but there's a lot of people who can't," said Chief Fleming. "Every second it's getting worse and worse."
Until finally, at 15 minutes and 40 seconds, the Ionization Detector sounds.
That's more than seven minutes after the Photoelectric Detector went off.
Those are minutes firefighters agree, could be the difference between life and death.
And these once-skeptical fire experts admitted they were stunned.
"That was a real eye-opener," said firefighter Danny Hunt.
"It's just amazing the difference in the two," said firefighter Jeff Huddleston.
"I thought once that first one went off, the other two would follow suit and I was really shocked," said Mike Turner.
The makers of the Ionization Smoke Detectors say they work best with faster burning, flaming fires.
"We're going to light a flaming fire," said Chief Fleming.
So, we put the same three detectors to the test.
It wasn't long before all three alarms sounded.
"All of the detectors went off within seconds of each other," said Fleming.
That's good news, but remember, you are most likely o die in a smokey fire.
The same kind where Ionization Detectors may fail to go off until it's too late.
"I think since 1990, the failure to recognize this problem is responsible for literally thousands of needless deaths," said Chief Fleming.
"That's a lot of lost lives right there," said Mike Turner, representative for the Nashville Metro Fire Department
After seeing our test, Turner said he's making the switch to Photoelectric.
"The technology is out there to save your family, and that's the bottom line," he said.
Our tests were not scientific.
But federal government scientists have conducted their own tests and they found a difference of as much as 30 minutes.
That's why some key fire prevention groups are now recommending that people switch either to Photoelectric or at least to a Dual sensor that's both Photoelecric and Ionization.
Photoelectric Detectors do run about five or six dollars more than Ionization Detectors.
You can find out about an East Tennessee family who wishes they knew about the difference between smoke detectors before the house fire that killed four of their children, by watching Part 1 of this series called "Smoke Detectors Part 1: They Have a Potentially Deadly Difference," which is linked below.
You can also get more information about smoke detectors and the difference between them on the U.S. Fire Administration's website by clicking the link below.