The signs, still posted in and around various Harvard houses after summer construction, warn ominously of asbestos removal efforts.

But students can rest easy; the asbestos cleanup over the summer was precipitated by a need to replace old equipment in rarely-used boiler rooms and does not represent a danger to students or employees, University maintenance officials said.

Asbestos--a fibrous mineral--was widely used as insulation during the mid-1900s. When its dust was found to be carcinogenic in the '60s and '70s, the insulation quickly fell in popularity.

Still, the material can often be found in older buildings, and by the '80s, health fears had spawned the new industry of "asbestos abatement."

At Harvard, many of the older classrooms and Houses were once insulated with asbestos, although the majority of the insulation was replaced long ago.

"Harvard's had an asbestos abatement program in place for more than a dozen years," said Philip W. Bisaga, the mechanical maintenance manager for the office of physical resources. "We've gone way beyond all code issues in asbestos abatement."

This means that no asbestos can be found in any of the areas that are widely used by either students or maintenance personnel. Most of Harvard's rooms have long been free from asbestos insulation. The remaining asbestos is mostly in unfrequented boiler and control rooms.

"The leftover asbestos can't cause any danger unless it's disturbed and the fibers are airborne. We aren't even obligated to replace it," said Gene G. Ketelhohn, the building manager in the houses.