Furnace / Duct Insulation
Roll of ACM insulating paper
ACM "tape" on seams of air plenum, painted over
Here are some samples of how asbestos-containing materials (ACM) were used to insulate furnaces and ducts. Typically the material used was an asbestos-containing paper. The paper came on an 18″ roll for large areas, and also on a 2″ roll, like a roll of tape. Either the material was sprayed with water and then applied, or an adhesive was applied to the duct or furnace first, and then the paper or tape was applied over the adhesive. In some cases, only the seams of the ducts had the “tape” applied. In other cases, only the seams of the “return” ducts were taped and the entire “supply” duct was totally wrapped with this asbestos-containing material.
These ducts usually are fed from a forced air “octopus” furnace. These furnaces were very popular and at the time, very cutting-edge. The furnace is usually only insulated on the upper portion (the “head”) where the fan “forces” the air through the duct work.