All fuel-burning appliances in your property produce carbon monoxide (CO), including gas furnaces. Normally, the gas is carried out of your home, but sometimes things go wrong and you can end up with a dangerous leak. According to the Centers for Disease Control and Protection, CO leaks can lead to poisoning that causes flu-like symptoms and is capable of killing a person (http://www.cdc.gov/co/faqs.
Since this gas has no odor or color, it’s virtually undetectable by human senses alone, which is why it’s so important to have working and properly installed CO detectors in your property.
What you should do
•    Place a detector on each level of your home for maximum protection.
•    Make sure all detectors are five feet from the ground, where they get the most accurate readings of your home’s air.
•    Have one detector near every sleeping area. It’s vital that people can hear the devices if an alarm goes off when everyone is asleep.
•    Place a detector near any attached garages you have. A car can produce CO anytime it is running, and those gasses can pass from the attached garage into your property.
•    Follow the manufacturer’s recommendations for installation and placement. Each model is tested according to the specifications of its maker, so you want to take that into account.
What you shouldn’t do
•    Don’t place detectors close to a fuel-burning appliance as you could end up with false alarms.
•    Avoid placing them in very humid places like your bathroom because that could mess with the sensor.
•    Keep the detector out of direct sunlight. Extreme temperatures shorten its lifespan and/or cause poor performance.
•    Don’t install detectors by sources of blown air, such as an open window, because the inside air reading won’t be accurate.
What to buy
Carbon monoxide detectors come in more than one style. The most common is the alarm or detector, which works like fire and smoke alarms. These devices alert you when they sense a dangerous CO level in your property’s air. Monitors, on the other hand, actively gauge the level of CO in the air and provide a digital readout.
A traditional alarm may work fine for your property if it’s correctly installed, but if you suspect there’s a problem or could be one in the near future, spring for the monitor. A monitor will show you when levels are rising, even if it’s not yet at the level that would cause a typical detector to sound.