With threats from asbestos, radon and lead poisoning, we have enough to worry about in and around our homes; asbestos floating down from the ceiling, radon rising up from the basement and lead-impregnated water gushing from our faucets.

There is yet another source of worry. If your home is heated by a gas or oil-fired furnace, your water heater or clothes dryer is gas fired, your cooktop or oven is gas operated, you have a fireplace or a wood-burning stove, you may be exposed to carbon monoxide (CO) poisoning.

CO is a by-product of combustion. Therefore, anything in your home that uses a flame produces carbon monoxide. In most instances, proper ventilation, and well-maintained appliances can prevent the problem. But, since carbon monoxide is a tasteless, odorless, invisible gas, its presence is difficult to detect.

Carbon monoxide poisoning accounts for half of the poisoning deaths that occur each year in America. Depending on whose statistics you apply, the fatality count ranges from 200 to 1,500 deaths a year.

Carbon monoxide is dangerous to humans because it has an unusually high attraction to hemoglobin, which is the main component of red blood cells. As a matter of fact, its attraction to hemoglobin is 245 times greater than the attraction of oxygen to it. Oxygen doesn't have a chance of getting into the blood stream if enough CO is present.

If you and your family feel tired and listless around your home, and much better when away, this could be a sign of carbon monoxide poisoning. CO poisoning is difficult to diagnose because its symptoms are much like those of the flu. Low-level exposure symptoms can include: headaches, fatigue, nausea, dizzy spells and confusion.

To protect yourself:

First, hire a licensed heating contractor to check your furnace and exhaust ducting. A cracked heat exchanger could allow CO into your house via heat inlets. Do this before the heating season.

Next, make sure that chimneys, flues and exhaust ducts for all gas appliances are clean and clear, so that CO has a path to leave the home. Also, make sure that all gas appliances have plenty of fresh air available to them so that they aren't using your oxygen to do their job properly. This should also be done before the heating season begins.

Finally, make sure your garage is properly vented. A leaking auto exhaust in a poorly ventilated garage can fill a home with CO in less than five minutes.

It is not wise to burn kerosene lamps, grills, and portable gas heaters inside the house. These kinds of appliances create CO, but don't come with a method of exhausting it outside of the home.

CO is invisible, tasteless, colorless and occurs to some extent in every home in America. So, how can you tell when danger exists other than becoming ill?

There are two ways: chemical detectors and electronic detectors.

The least expensive of the two detection methods uses a chemical coating that changes colors as the content of carbon monoxide increases. These detectors can be purchased for about $10 and must be replaced annually. You must also be committed to checking them on a regular basis to see if the color has changed.

The second way is a bit easier. That's because it is electronic. Carbon monoxide detectors are now available on the open market. Next time you purchase a smoke detector, upgrade to one that has a carbon monoxide detector built into it. Believe it or not, there are smoke detectors that detect excessive amounts of smoke, carbon dioxide and natural gas (methane). You'll end up with less gadgets on your ceiling.