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.
1) Build the chimney as tall as you can. Use a chimney pot to make it even taller without adding to a top-heavy looking mass. Most fireplace books assume 15 feet from hearth to top of chimney is sort of a minimum. Old houses tended to have taller chimneys (because they worked better) than modern houses.