Install a carbon monoxide alarm on every level of your home and outside sleeping areas. Test them monthly and replace them every 5–7 years.
Symptoms of CO exposure include headache, dizziness, nausea and confusion, often in several people at once.
If your CO alarm sounds: leave the house immediately with everyone, including pets, and call 911 from outside. Don't go back in until responders say it's safe.
An annual furnace tune-up includes a heat exchanger inspection and carbon monoxide test.