A few weeks after we instructed a caller on our radio show how to test the pressure-and-temperature relief valve on his water heater, we got an irate letter from a listener who had attempted the test we had recommended. She was upset because a leak resulted, and her plumber charged her $46 to replace her pressure valve. As it turned out, it was a good thing the listener had discovered that the valve was frozen shut. In such a condition a water heater can explode with the force of a couple of sticks of dynamite.

During a recent survey of more than one thousand homes, 20 percent of the pressure-and-temperature relief valves examined were not operational. In other words, one out of every five homes might be in danger of a serious explosion if action is not taken.

That thought introduces this week's topic, "home inspections." These inspections are critical in making your home safer for you and your family.

Many people believe that an inspection is performed only before the sale of a home. That's great for the buyer, but what about the time that you own the home? What about your safety and that of your family while you are living there? When it comes to your safety, a home inspection by a professional is prudent.

The survey mentioned earlier also found that 43 percent of homes more than 30 years old, 27 percent of homes 13 to 24 years old and 10 percent of newer homes all had electrical system deficiencies, including inadequate or faulty wiring. A faulty electrical circuit can easily cause a house fire.

Gas appliances, such as faulty fireplaces, furnaces and cooking appliances, were found to promote the presence of carbon monoxide. It is estimated that 1,500 deaths each year are attributed to carbon monoxide poisoning from gas appliances in the home and those used for camping. Other potentially dangerous problems include: cracked heat exchangers in furnaces, blocked flues, incorrectly installed pressure-and-temperature relief valves on water heaters, lead paint and electrical system inadequacies.

It isn't only poisons that a professional home inspector can help you discover. An inspector can tell the difference between "normal" settlement cracks and those that indicate a structural defect. A crack in a wall or in a foundation might appear to be nothing more than normal house movement. A well-trained eye can detect the onset of a serious structural problem.

Don't overlook cancer-causing building materials. Homes built between 1920 and 1960 might contain asbestos in insulation, ducting, pipe coverings, flues, floor tiles and roof covering materials.

Most home inspection reports will not address specific repair methods or include information about aspects of the condition of the home that require the services of an individual with specific expertise (such as a soils engineer or structural engineer). Don't expect too much from the inspector. Even the most qualified will be limited in his ability to provide certain technical information.

Not all of the information in an inspection report is negative. Such a report can include positive input concerning the condition of a home, as well as the type of maintenance that will be necessary to keep it in tiptop shape.

The most qualified home inspectors are those with years of building experience, such as general building contractors, architects or engineers. They possess an understanding of the various aspects of construction, and are most likely to offer the most comprehensive and legitimate report.

An inspector who is certified by the International Conference of Building Officials (ICBO) and/or a member of the American Society of Home Inspectors (ASHI) offers an added level of assurance that the inspector is well qualified.

ASHI, a nonprofit voluntary professional association, has developed formal inspection guidelines and a professional code of ethics. Members of ASHI are independent professionals who operate their own inspection services from coast to coast. In addition to providing information about their association, they offer consumer publications explaining home inspection and, upon request, will provide a membership list for specific geographic areas to assist with the selection of a home inspector. ASHI can be contacted at 1-800-743-ASHI.