Insulation blankets (the outside covering or shell), door gaskets, duct insulation, and tape at duct connections of furnaces and boilers all may contain asbestos.  Oil, coal, or wood furnaces with asbestos-containing insulation and cement are generally found in older schools, its installation dating between 1920 and 1972.  The material is white or gray in color and resembles the plaster used in casts to protect broken bones.  If the furnace insulation is in good condition, it is best to leave it alone and keep maintaining it in good condition.  If the insulation is in poor condition (friable), or pieces are breaking off or it has been subject to water damage, you should have it repaired or removed entirely.

You may want to have the entire furnace replaced by a more modern efficient model.  You should first find out if the insulation actually contains asbestos by sampling and analysis.  While the insulation is in poor condition and awaiting repair or removal, children should be prevented from playing in or near the space to protect them and prevent further insulation damage.

Steam and hot water pipes were insulated with asbestos-containing material, particularly at elbows, tees and valves.  Its appearance is similar to that found on boilers.  Pipes may also be wrapped in an asbestos "blanket", or asbestos paper (which looks very much like corrugated cardboard).  Asbestos-containing insulation has also been used on and inside round and rectangular furnace ducts.  Sometimes the duct itself may be made of asbestos-containing materials.

If you have moderately damaged insulation around pipes or boilers, the best current recommendation is to leave the insulation in place and have the protective covering repaired.

Asbestos-containing cement sheets (CAB), millboard, and paper have been used frequently as thermal insulation to protect the floor and walls around wood burning stoves.  Again, there is no hazard if left as is, if it is in good condition.