QDEAR BARRY: Our water heater and forced-air furnace are installed on the same raised platform in our garage. Recently, the water heater began leaking and had to be replaced. Our main concern involves the water that leaked into the platform and the adjacent wall. The enclosed space below the platform is part of the duct system for the furnace and we're worried about the long-term effects of this moisture. It seems strange that the joint use of the platform would ever have been allowed, considering the potential for mold and other moisture-related problems. Is it okay just to repair the leak, or should the platform be opened up to promote more thorough drying? -- Lisa

ADEAR LISA: Water heaters and forced-air furnaces are commonly installed side by side on raised platforms in garages. The potential for moisture-related problems should be obvious, but in most cases, little or no thought is given to eventual leaks from the water heater. The obvious solution is so simple and inexpensive that it's a wonder it is seldom practiced. All that is needed is an overflow pan, commonly known as a Smitty pan, installed under the water heater, with a drainpipe to carry water from the pan to the outdoors or at least to the garage floor.

In most cases, the raised platform serves as a passageway, known as a plenum, for the air that recirculates from the house to the furnace. If the interior of the plenum becomes wet, mold or fungus can develop and can hurt air quality within the house. Therefore, you should dry the platform immediately if there is a leak. To do this, run the furnace blower, along with additional fans in the garage. You can also hire a company that specializes in moisture removal and water damage repair.

Once the plenum has been dried, an inspection by a qualified mold specialist would be wise.

DEAR BARRY: Our fireplace is equipped with natural gas to help ignite the logs. Is there any requirement to keep the damper open in case of a gas leak? -- Nicole

DEAR NICOLE: Dampers must be fastened open when fireplaces are set up with gas-log systems that have cement logs. With wood-burning fireplaces, this requirement does not apply. The reason for securing the damper is not to protect against gas leaks, but to prevent combustion exhaust from venting into the house. Natural gas has a commonly recognized odor that you would notice if the log lighter leaked. Exhaust from burnt gas, however, can go undetected and therefore constitutes a more significant hazard, especially because exhaust from gas logs may contain carbon monoxide.

In older homes, gas logs may have been installed before the requirement to secure or remove the damper. In those cases, a special clamp can be added to the damper as a safety upgrade.

Barry Stone is a professional home inspector. If you have questions or comments, contact him through his Web site, www.housedetective.com, or send mail to 1776 Jami Lee Court, Suite 218, San Luis Obispo, Calif. 93401.

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