According to the Consumer Product Safety Commission (CPSC) about 200 Americans die each year from carbon monoxide (CO) poisoning associated with home heating equipment. Scores more are injured.

CO is so highly toxic because it chemically binds to hemoglobin and rapidly displaces oxygen in the blood. This causes the body’s brain, heart, and other tissues, muscles and organs to become oxygen starved. The most common symptoms are headache, fatigue, dizziness, nausea, vomiting, trouble thinking, poor concentration, vision problems, shortness of breath and heart palpitations. Not surprisingly, it is often misdiagnosed as a cold or the flu.

A forced-air furnace takes heat produced by combustion and transfers it to the air through a piece of metal called a heat exchanger. The warmed air is then circulated into a home through supply ducts. The products of combustion, carbon dioxide, water vapor and carbon monoxide exits through a vent or flue pipe. Forced air gas furnaces pose the greatest risk. If an oil furnace is leaking CO, the foul odor of oil combustion will generally warn people of the danger.

The furnace heat exchanger consists of a highly conductive metal that transfers the heat of combustion to the air circulated throughout the house. If the heat exchanger rusts, corrodes or cracks, CO can be allowed to enter the home.

Equipment defects, improper installation, lack of maintenance or a combination of these factors can all cause a furnace to produce too much CO.

Because of the sophistication of most home heating equipment, a professional technician should routinely inspect and service it.

An inspection for a gas-fired furnace should include the following:

• Clean and change filters.
• Clean combustion chamber.
• Check and adjust burners and burner safety control; check color of the flame. It should be blue, not yellow.
• Check ignition system. Measure amount of CO in flue gases.
• Clean and lubricate blower and motor.
• Clean and check heat exchanger for leaks by injecting chemicals or a "smoke bomb" to see if anything escapes the system.
• Inspect chimneys, vents and flues for deterioration, corrosion and blockage as well as secure fittings.

The CPSC also recommends installing two CO detectors - one above the furnace, the other outside the bedrooms.