DENVER (KDVR) — Denver will test the city’s Outdoor Warning Sirens on Wednesday, May 10 at 11 a.m. The siren may be heard throughout the city and at the Denver International Airport.

Additionally, tests for the landline and opt-in Reverse Emergency Notifications (REN) system will begin on Monday. The tests will then continue every day of the week through Friday.

When the tests will happen will depend on the neighborhood. A list of the REN schedule can be found here.

The city said the test is only meant to ensure the emergency technology functions, so people should not be alarmed.