After the tenant left his apartment, the heater ignited nearby bedding materials, said Bill Ruchti, Janesville Fire Department shift commander.
Another tenant in the three-apartment complex reported the fire just before 9:30 a.m.
The second tenant heard smoke alarms going off and smelled smoke, but called someone else before dialing 911, Ruchti
Fire officials want residents to call 911 when they hear smoke alarms.
"Seconds are critical when it comes to a fire," he
also reminded residents to take precautions when using space heaters.
"First and foremost, don't leave them on when you're gone or (a home is) unattended," he
Utility crews hoped to have furnaces in the building up and running soon so the tenant in the ground-level apartment wouldn't have to relocate, Ruchti