You need at least one carbon monoxide alarm in your house.
State law now requires CO detectors in most older homes, all new homes, as well as all apartments and condos.
"A carbon monoxide alarm is sniffing the air 24 hours a day and it will give you advanced warning," says John Drengenberg at Underwriter's Labs. "It's a very sophisticated device."
Drengenberg says CO monitors are normally placed on the ceiling to keep them out of the way. But they can go anywhere in the house, high or low.
"That's because carbon monoxide fills the entire living space rather equally."
The key is to have a Carbon monoxide monitor - a UL listed monitor - on every level of your home.
"Most importantly, have it outside the sleeping areas. So if it goes off in the middle of the night you can hear it very well."
If the alarm does go off: open the windows, call 911 and get outside into the fresh air right away. Don't go back inside until emergency help arrives.
For more information
Carbon Monoxide Alarms FAQ
Consumer Reports: CO & Smoke Alarm Buying Guide