Good Question: How Do Tornado Sirens Work?

MINNEAPOLIS (WCCO) -- People across Hennepin County got an unexpected wake-up call Tuesday morning -- sirens sounded just after 6:00 a.m., but turns out it was an accident and there was no emergency.

That got us wondering: How do tornado sirens work? Good Question.

If you live close enough to one of Hennepin County's 242 sirens, it's almost impossible not to hear them. And it makes you wonder who's pushing the button that's grabbing our attention.

"It's a local decision that's made," Minnesota's director of Homeland Security and Emergency Management Joe Kelly said. "And there's a button that gets pushed if you will at the county level," said Joe Kelly.

Kelly said in most counties -- Hennepin included -- the sheriff's office is in charge of sounding the sirens.

"They are computer based systems. As a whole system they are connected through the telephone system," Kelly said.

A ticker from the National Weather Service comes into dispatch letting them know it's time to trigger the sirens. Hennepin County's system has become even more computerized over the past few years, and a computer hardware malfunction is to blame for Tuesday morning's false alarm.

False alarm or not, Kelly wants you to take cover when you hear that familiar sound.

"We have to condition ourselves to take the same action every time we hear one of these warning sirens. We need to take cover first and then tune in to find out what's going on," Kelly said.

Kelly said the sirens aren't just for tornadoes -- they were installed after World War II during the Cold War in case we were ever invaded. Now they can be triggered for HAZMAT emergencies, fires, and of course severe weather.

Officials have the capability of triggering just one alarm, or alarms for just one city. But Kelly said typically they operate the sirens by zones.