Some fireplace inserts have heaters to complete the illusion and heat the space. Most fireplace inserts operate from normal 120V electric outlets. Have two blocks under the fireplace insert mounting frame and another two blocks higher than it. Screw the blocks into place in the studs. Retain Air Vents Clear: https://fireplace-mantel47779.blogozz.com/27700771/fireplace-cleaning-for-dummies