Your chimney may look good on the outside, but have hidden dangers on the inside. Damaged chimney liner? HeatShield® can restore your chimney's clay flue liner and save you the expense of rebuilding or relining with a stainless steel chimney liner. HeatShield is a chimney liner repair system that eliminates the hazards and draft problems caused by gaps, cracks and spalling in otherwise sound masonry chimneys. HeatShield Cerfractory Flue Sealant is a professionally applied product available through our factory trained chimney professionals.