Furnace safety sparks feud

DEAR BARRY: You are part of a large group of folks who misunderstand the effects of a cracked heat exchanger in a forced-air furnace. The supposed "threat" of carbon monoxide is perpetuated by members of the heating industry who have managed to rope in many utility companies and home inspectors in promoting this fear.

When you consider that the heat exchanger is on the outlet side of the blower, it is more likely that circulating air would enter the exhaust stream than exhaust would enter the air stream and the home. This is the conclusion of a new study, but that information has apparently not come to your attention. --Dave

DEAR DAVE: According to a wise philosopher (Dennis Prager), scientific studies do one of two things: They agree with common sense, or they are wrong. In this case, common sense reflects what is routinely observed in furnaces with cracked heat exchangers. There are abundant cases of people having been hospitalized or having died from carbon monoxide (CO) exposure, where the source of CO was determined to be holes or large cracks in a heat exchanger.

From a scientific standpoint, the process is elementary. A heat exchanger is a metal container with a gas burner inside. When the burner is lit, the metal container becomes hot. Air is blown across the outer surface of the hot container, the air becomes warm, and the heated air is blown into the living areas of the home.

Meanwhile, the exhaust fumes inside the metal container rise through a chimney, known as a flue pipe, and exit at the roof. As long as the exhaust does not mix with the warm air, occupants of the home remain safe.

However, if the hot metal container has cracks or holes, combustion exhaust can enter the warm air stream in the following manner: ...CONTINUED

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