Causes and Prevention for Carbon Monoxide Poisoning Carbon monoxide is poisonous to humans and animals. Learn the warning signs to prevent CO poisoning. A clear and odorless gas, carbon monoxide (CO) is poisonous to humans and animals. Carbon monoxide is both naturally occurring and a byproduct of manmade combustion. Defective furnaces, fireplaces, flues, and oil heaters are most frequently responsible for accidental carbon monoxide (CO) poisonings. When improperly vented, malfunctioning home appliances like furnaces and air-conditioners can slowly fill your home with CO.In the United States, CO leaks are responsible for an estimated 400 deaths a year and more than 20,000 trips to the emergency room, according to the Centers for Disease Control and Prevention (CDC). However, as CO poisoning often goes unreported, the number of instances is most likely much higher.How to spot carbon monoxide buildupdecreased hot water supplyincreased moisture on windowsloose or disconnected chimneyfireplace or applianceblack soot on appliances and ventsrust or water on vents or chimneyloose or missing furnace panelWhat are some signs of carbon monoxide poisoningCO is dangerous because there tend to be no noticeable symptoms if an individual's CO levels are at less than 10% in the bloodstream. Above 10%, CO poisoning symptoms may mimic the flu or a cold. At that level, according to the Mayo Clinic, symptoms may include:Low to moderate poisoning: headachefatigueshortness of breathnauseadizzinessSevere poisoning: confusionvomitingloss of muscle coordinationunconsciousnessHow might you prevent carbon monoxide poisoning?Taking a small amount of time to manage your home's risks will greatly protect you and your family.Have your furnace inspected and maintained by a qualified contractor once a year. This should be done before the start of the heating months.Have your gas appliances inspected at the same time as your furnace to ensure they are operating correctly.Keep in mind that space heaters, ovens, portable generators, and other gasoline-powered engines can cause a buildup of carbon monoxide.If you suspect the appliance or tool you're using might be causing a buildup of CO, play it safe and open a window. If you're working in the garage, open the door. Ventilation is a sure way to disperse a buildup of the gas.Carbon monoxide detector placement in your homeIn addition to smoke detectors, install a CO detector on each level of your home, and in or near each sleeping area. You can also hook them up to a smart home system to send a message to your smartphone if it is detected when you're not at home. While you shouldn't rely solely on CO detectors, having them properly placed throughout your home can serve as a good fail-safe.Try to keep the detectors at least 20 feet from any fuel-burning appliances and at least 10 feet from high humidity locations like bathrooms and kitchens, as moisture can sometimes trigger faulty readings. Test the batteries of your detector regularly, and if an alarm sounds, call a professional to check your gas-burning appliances.What do I do if my carbon monoxide detector goes off?Exit the house.Check everyone for signs of carbon monoxide poisoning.Call 911.Do not re-enter your home until authorities have cleared it.Visit the CDC website for more information about carbon monoxide poisoning.Enlarge infographic .