South Dakota Fire Marshal Paul Merriman says people should check the smoke-alarm batteries in their homes to mark the change from daylight savings time to standard time.
The switch was official at 2 a.m. Sunday.
Merriman says that in addition to setting their clocks back an hour, people should check their smoke alarms and carbon monoxide detectors.
The state fire marshal says that a majority of deaths in home fires could be prevented if all homes had working smoke detectors.
Merriman says smoke detectors have a test button. When that button is pressed, it should make a sound to indicate the batteries are fine.
Merriman says anyone who doesn't have a smoke detector should install one.