Never ignore an alarm! It is very possible that you won't be experiencing symptoms of CO poisoning when the alarm sounds. That doesn't mean there is no carbon monoxide present. The alarm is designed to go off before may you feel sick, so you have time to react and take action.

Don't panic. Press the Mute Button to temporarily quiet the alarm, then call 911 or the Fire Department. Immediately move everyone to a source of fresh air. Moving outside is the safest solution.

Leave the CO alarm where it is (The emergency responders will want to check it when they arrive). Do not re-enter your home until the emergency responder has arrived, your home is aired out, and your CO alarm returns to normal operation.

Have the problem corrected as soon as possible. Keep your home well ventilated until the problem has been fixed.

In some cases, problems can occur even if all appliances are working properly:

• If appliances, flues and chimneys are confirmed to be in good working order, the source of carbon monoxide may be from backdrafting. This condition exists primarily in newer, more energy efficient, "airtight" homes. Flue gases normally vent to the outside through flues and chimneys. As temperatures drop at night, air pressure inside an airtight home may become lower than outside, causing flue gases that normally exit the house to turn around and flow back down the pipes.

• Inadequate air supply in a room where two or more combustion-driven appliances share the same air source, such as a water heater and furnace in a utility closet, can create a more complicated form of backdrafting called reverse stacking. This occurs when one appliance turns on, such as the furnace, and is unable to get adequate fresh air. When the furnace operates, it draws contaminated air from the water heater exhaust, and spreads polluted air throughout the house.

• A broken thermostat can keep the furnace running continuously, depleting the oxygen supply inside the house. This may lead to backdrafting.

• In multiple family dwellings like apartments or townhouses, where living spaces share walls and pipes, carbon monoxide from one unit may go into a neighboring space through floorboards, cracks, or underneath doors.