Hidden dangers can make homes deadly.

The death of tennis star Vitas Gerulaitis from carbon monoxide poisoning highlights the hidden dangers that may be present in homes. Serious defects in the different systems in a house, hidden as well as visible, can be found in 40% of the nation's housing (at the time of resale), according to HouseMaster, a national home inspection firm.

According to Kenneth Austin, the company's chairman, "Relatively few of the deficiencies found in homes for sale are life-threatening, as with carbon monoxide poisoning. Having a home professionally inspected, however, will help uncover existing or potentially dangerous situations--as well as those that, while not dangerous, can be `pocketbook threatening' and cost the new homeowner thousands of dollars to repair."

Some of the most common defects are deficiencies in the central heating and cooling systems, lower-level water seepage, roofing, electrical systems, and plumbing problems (including poor water pressure). The most potentially dangerous situations--not obvious to the untrained eye--include cracked heat exchanges or blocked flues, which can lead to carbon monoxide leakage; improperly installed hot water heater relief valves; and electrical system inadequacies that can become fire hazards

Of the three, electrical system deficiencies are the most common. A national HouseMaster study of 1,000 homes found them in 43.7% that were 30 years old and up, in 27% of those 13-29 years old, and in 9.5% of homes one to 12 years old. "Deficiencies in the electrical system of a house are rarely visible to the layperson," Austin notes, "yet they are the major cause of home fires. A trained home inspector, however, will systematically look for signs of inadequate or faulty wiring and provide the customer with guidelines on what the necessary repairs are and what they will cost." Even something as simple as an inadequate number of electrical outlets can lead to overloading of existing ones, and ultimately can become a fire hazard.

"When buying a house, you want to look the 220-volt service and at least 100 amps with a disconnect switch at the panel box. The...