The first and only condensing vented gas fireplace system certified for use in the United States. This super-efficient, ecologically sensible gas fireplace is so unique, it humidifies as it heats. The concealed three-stage heat exchanger captures more than 90 percent of the heat energy from the burner and directs this warm air into your home - not up the flue. With so much of its heat extracted, the exhaust can be vented outdoors in conventional PVC piping - saving money, labor, and space on installation compared to traditional direct-vent systems. The Mantis unit is so versatile it can be installed as a fireplace, insert, or freestanding stove, leaving you many options to have this great product a part of your home.