Fireproofing is the process of applying a thermal barrier, a cementitious fire protective coating specifically formulated for application over rigid, urethane and polystyrene foam plastics. Spray applied to interior foam surfaces on walls and ceilings Z-3306 forms a hard, durable, monolithic thermal barrier against heat and fire. Must be applied to any area where a heat source is present, if you as a homeowner do not apply the coating your insurance company may not insure as this is not in compliance with the building code.