Ask local agency for advice on formaldehyde-foam threat

Q. We happen to be one of thousands who insulated their homes with the now-banned formaldehyde foam. We do not feel that the drastic step of ripping out interior wallboard to remove the insulation is needed. We do, however, like the idea of adding some type of air-filtration system which brings in fresh outside air during months when the house is closed. Do you have any suggestions? Are existing heating systems actually able to filter out formaldehyde fumes?

A reader Rockville, Md.

A. Formaldehyde-foam insulation originated in Europe and became a fad in the United States some years ago. An excellent insulator, the material was subsequently banned by building and health departments for its toxicity.

Especially toxic during a fire, the material is otherwise most toxic during the 30 days after installation. We understand residual fumes may thereafter be present in the house. We are told that finishing the inside wall and ceiling with Glidden Sealer may inhibit fumes.

For definite information on this formaldehyde-insulation matter, contact your local health department for its experience and recommendations. More information can be obtained by looking under ''Poison Control Centers'' in the Yellow Pages, and by contacting the US Environmental Protection Agency.