Neighbors rang the doorbell several times, but no one answered the door. Then the emergency services were called in. The fire brigade arrived on the scene and tried to gain access to the house through a window on the first floor.
Then it turned out that the sound did not come from a CO detector, but from an alarm clock. The resident of the house got up early to go to work, but had forgotten to turn off the alarm. This one had gone off again and did so with quite a bit of volume.
Neighbors called the resident of the house and he quickly rushed home. The man turned off his alarm clock and then peace returned to the street.