What is a sealer mastic primarily used for?

A sealer mastic is specifically formulated to seal and encapsulate materials, with a significant application being the containment of potentially hazardous fibers, such as those found in asbestos. When mastic is applied to these materials, it effectively prevents the fibers from becoming airborne, thus reducing the risk of exposure which is crucial for safety in environments where such materials are present. This sealing capability is key in managing the risks associated with asbestos, which is a serious health concern.

In contrast, the other options do not entirely capture the primary function of a sealer mastic. While enhancing aesthetic appeal or acting as an adhesive for fittings are possible uses of different materials, they are not the main purpose of sealer mastic. Similarly, while it could have a role in repairing damaged insulation, its primary role focuses more on sealing and containing hazardous fibers.