Every year, carbon monoxide (CO) kills 200 to 300 Americans and poisons more than 5,000 others. This poisonous gas — which can't be seen, tasted, or smelled — can originate from a wide variety of sources, including a car or lawn mower left running in an attached garage, improper venting of a kitchen range, or a cracked or disconnected vent pipe for a combustion appliance (see illustration above). As construction technology has advanced, the danger of carbon monoxide poisoning has actually increased. Chimneys in tighter, energy-efficient houses are more likely to backdraft, and high-efficiency heating units now produce cooler flue gases that are less likely to vent naturally. Consumer awareness is
