The Denver skyline and the Rocky Mountains.

(Hart Van Denburg/CPR News)

A mobile alert will be issued in Denver to a million residents and visitors in the area Wednesday, Sept. 5. 

This test is unique because it’s the first time the system will be used across all municipalities in the Mile High City, said Daniel Kolb, an emergency coordinator with the city’s Office of Emergency Management. The alert will reach the entire city and county of Denver, including those at Denver International Airport. 

“Most local municipalities and local governments haven’t had an opportunity to test the system and reach a million people,” Kolb said. 

Folks will receive a loud noise and vibration on their mobile devices between 11 and 11:30 a.m. The message will also indicate the alert is only a test and will be repeated twice. 

People who have a tablet with data on it may also receive the alert. Flip-phones and smartphones older than 2012 most likely won’t receive anything, Kolb said. Some smaller carriers may also not carry the alert.

The Federal Communications Commission launched the Wireless Emergency Alert system nationally in 2012 and more than 33,000 alerts have been sent to cell phones nationwide, warning people of dangerous weather, missing children and other critical situations.