The Comfort Glow Natural Gas (NG) multi-plaque, manual controlled units will heat your spaces on even the coldest days and can be used in bedrooms. The modern design features high quality ceramic plaques that radiate soothing, direct, immediate infrared heat. This heater is 99% fuel efficient. It requires no duct work or other venting and includes a built in oxygen depletion sensor. The sleek design and neutral color fits any decor. Due to the built in oxygen safety sensor, vent free products may not work properly at elevations above 4,500 Ft.