How safe are chemicals used to melt ice, and what about those unventedfireplaces?

Q. Is it safe to use Ice Melt with chloride to melt ice on the edges of our roofs and over our eaves troughs here in Michigan? What harm can it do to the shrubbery and wooden porches (floors) on which it falls upon melting?

- F.L., Charlevoix, Mich.

A. The chloride in Ice Melt is designed to generate heat. It is not concentrated in the mixture and is even further diluted when mixed with snow, says Dick Miller of Frank Miller and Sons, one of the largest manufacturers of ice-melting products in America. Mr. Miller says only if the runoff is concentrated in one spot, might problems occur.

Miller does recommend using heated coils in the gutter and along the roof, instead of Ice Melt, to dissolve ice. These can be bought in most home centers and hardware stores.

Chris Chang, a graduate student in organic chemistry at the Massachusetts Institute of Technology agrees with Miller. He says that if diluted, chloride is not dangerous and doesn't threaten shrubbery.

Q. We recently installed a gas-burning log insert in our brick fireplace. Several friends have raised health questions about the unvented device. Should we be wary of using this gas heater?

- F.M., Stroudsburg, Pa.

A. Unvented gas-burning inserts can be dangerous, according to gas technician and fireplace installer Bob Kilmartin of Millis, Mass. These devices burn at 99.9 percent efficiency, producing hardly any combustive byproducts. But when used without chimneys, any harmful material produced will circulate within the home.

Mr. Kilmartin's advice: Never use the insert in a bedroom. In other rooms, open windows or the flue if the device is placed in the fireplace. In some states, including Massachusetts, unvented inserts are illegal because of safety concerns.

Readers: Pose your questions and we'll seek out experts on home repairs, gardens, food, and family legal issues. Send queries to the Homefront Editor, The Christian Science Monitor, One Norway Street, Boston, MA 02115 or e-mail home@csps.com