There is a new code in town. New wood-burning fireplaces shall have gasketed doors and outdoor combustion air. • Masonry fireplaces ONLY - the code applies to NEWLY CONSTRUCTED masonry, wood burning fireplaces ONLY. It does not apply to existing masonry fireplaces. • Does not apply to factory built/zero clearance fireplaces - factory built fireplaces (Marco, Majestic, Heatiltor, Preway, etc.) are not included in this code • Reason for gasket is to reduce energy loss when fireplace is not in use - the ICC & HPBA have clarified that the purpose of the gasket on the doors is to reduce the amount of energy lost up the chimney when the fireplace is not in use. It is also meant to improve indoor air quality by reducing the number of pollutants entering the home by the chimney. It is NOT meant to create an air tight or sealed door to use when burning.