All six members of a family in Riverdale, Maryland, recently woke in the middle of a winter night, suffering from headaches and flu-like symptoms. They quickly headed to a nearby emergency medical clinic and were found to be suffering from acute carbon monoxide (CO) poisoning.

Firefighters rushed to the home, where they rescued the family’s dog and then tested the indoor air. Their tests confirmed CO levels in the house of 200 parts per million (any level higher than 35-50 ppm is considered unsafe). Investigators found that the elevated carbon monoxide levels were caused by a recently installed water heater in the home. Luckily, in this case, the family (and their dog) recovered, the water heater was fixed, and emergency workers installed a carbon monoxide detector in the home.

“The Invisible Killer”

Cases of carbon monoxide poisoning don’t always turn out so well. In fact, the U.S, Consumer Product Safety Commission calls carbon monoxide “The Invisible Killer.” The colorless, odorless and highly poisonous gas is responsible for 230,000 visits to hospital emergency departments every year. In an average year, 430 Americans die as a result of carbon monoxide exposure.

As the Maryland family’s case demonstrates, high-level exposure to carbon monoxide (known as acute exposure) can be dramatic and extremely dangerous. The result can be sudden, severe illness or even death. However, chronic exposure to lower levels of carbon monoxide over months or years can also cause a number of serious health problems, including frequent headaches, fatigue, dizziness, shortness of breath, nausea and mental fatigue.

Where does carbon monoxide come from?

Carbon monoxide is formed primarily by the incomplete burning of fuels such as wood, oil, coal, charcoal, natural gas and propane. It is released outdoors by combustion engines in cars, trucks and other vehicles. Carbon monoxide is also produced by industrial plants. Indoors, the sources of carbon monoxide include unvented kerosene and gas heaters, leaking chimneys and fireplaces, back-drafting from furnaces and water heaters, and other combustion sources. When combustion appliances inside a home are not correctly adjusted, levels of carbon monoxide can soar.

How carbon monoxide affects the body

Carbon monoxide is harmful when it is inhaled. It poisons the body by attaching to the molecules (hemoglobin) that normally carry oxygen in the blood. As carbon monoxide attaches to these molecules, less oxygen can be delivered throughout the body. The result is tissue damage or even death, as the heart, brain and other vital organs are affected.

Carbon monoxide poisoning can be halted and reversed when it is caught in time. But even in these cases, the heart, brain and reproductive processes can be permanently damaged.

Steps you should take

Prevention is the most important strategy for reducing the risk of carbon monoxide poisoning in your home. Here are some preventive actions you can take:

1. Keep combustion appliances in your home properly adjusted.Any fuel-burning appliances should be inspected by a trained professional every year at the beginning of the heating season.
2. Never idle a car in the garage, even if the door is open.Fumes build up quickly — even with the garage door open — and can quickly affect the living area of your home as well.
3. Never use a charcoal grill indoors or in attached garages.This includes never using these devices in a fireplace.
4. Never sleep in a room with an unvented gas or kerosene heater.The risk of carbon monoxide poisoning is greatest when you are sleeping, because you may not be aware of early symptoms until it’s too late.
5. Install a CO detector. A detector will warn you if carbon monoxide levels are elevated.However, do not be lulled into a false sense of security. A CO detector is a back-up, not a replacement for the suggestions above.

By taking action to monitor, reduce and control carbon monoxide levels, you can lessen the threat of this “Invisible Killer” in your home. For more information on the dangers of carbon monoxide poisoning and additional steps you can take to protect your household, visit www.epa.gov.