If you haven't had your furnace checked in a while, you may want to call a local heating inspector. Officials say it's very important to have it serviced at least every two to three years.
"As people close their doors and windows they want to check up for efficiency and also safety preventing carbon monoxide things like that," says Wisconsin Public Service employee Jim Rosenberg.
Carbon monoxide can be released into the air if your furnace is not properly functioning. It's caused from unburned gases in the combustion of a furnace. You can prevent this by installing a carbon monoxide detector in your home. If the gas is released, the detector will set off an alarm.