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.
First, the top of the chimney must be at least 1 metre above roof level to prevent excessive turbulence. Secondly, a good rule of thumb suggests that system height from hearth level to the top of the chimney should be at least 4.6 metres. It looks like you'll need at least 2 metres of chimney projecting from the roof.