You already know it's important to have a working smoke alarm on every floor of your home and in every sleeping area, but do you also have carbon monoxide detectors? Carbon monoxide (CO) is an odorless, invisible gas that can build up and reach poisonous concentrations in homes with poor ventilation. In the winter, when windows are closed, the risk is especially serious.

Fuel-burning appliances — ovens, space heaters, generators and engines — give off carbon monoxide. So do fires, whether controlled or accidental, and lit tobacco products. Most home CO detectors sound an alarm when the concentration of CO in the air reaches 70 parts per million for an hour. Nationwide, some 4,000 children per year go to the emergency room with flu-like symptoms caused by CO exposure from sources other than fire, and about nine children die from lethal doses.

Carbon monoxide attaches itself to hemoglobin molecules in the blood, crowding out oxygen. When saturated with carbon monoxide, the blood cannot transport oxygen to the brain. Early signs of CO poisoning include headache, nausea, dizziness and possibly drowsiness or confusion. At higher concentrations or longer exposures, a victim will lose consciousness and, if not treated, die.