The vacuum tube in a CRT can implode if it is broken or punctured. The surrounding air will rush violently into the unsealed vacuum in the CRT, spraying broken glass in every direction. Color CRTs may contain mercury or other potentially toxic materials.
Instructions. Build a hearth for a fireplace that is 16 inches deep, according to This Old House writer Harry Sawyers. This is the standard requirement for municipalities and homeowner associations. The hearth should also extend a minimum of eight inches on either side of the fireplace.
Install the hearthstone. The hearthstone is the lip of your fireplace opening, perhaps the focal point of your outdoor fireplace. Installing it correctly is an important part of building an outdoor fireplace. 1  Place mortar in three 3/4-inch deep strips, 1 inch (2.5 cm) from each other.2  Set down the hearthstone, using a rubber mallet and level to make sure that it's plumb and level. 3  If the hearthstone isn't flush with the firebox, that's okay.onnect your gas-burning fireplace to the gas line. If building a gas-burning fireplace, prepare to hook up gas to your fireplace in order to get it working. 1  Turn off the gas. 2  Use plumber's putty on the threads of the main line to connect it to the flexible lines.