Hansen's disease, also known as leprosy, is a chronic bacterial disease that primarily affects the skin, peripheral nerves and upper airway.ansen's disease, also known as leprosy, is a chronic bacterial disease that primarily affects the skin, peripheral nerves and upper airway.
1 Direct-vent gas fireplaces cost $1,000 to $3,500, plus $500 to $1,000 for installation. 2  The cost of a ventless gas fireplace is $500 to $2,500, and while there are additional installation costs, you may pay extra for finish work (such as a mantle, marble surround, etc.). The cost of a ventless gas fireplace is $500 to $2,500, and while there are additional installation costs, you may pay extra for finish work (such as a mantle, marble surround, etc.).
1 Ventless (also called vent-free or unvented) gas fireplaces don't need a chimney or vent, and are either zero clearance (right against a wall) or close clearance (a few inches away). 2  They cost about $400-$1,500 plus installation of the gas lines and any desired mantle or surround. They cost about $400-$1,500 plus installation of the gas lines and any desired mantle or surround. 2  Some states do not allow the use of ventless fireplaces or restrict their use. 3  Some ventless models require you to keep a window open while using the fireplace.