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.
hearth. 1  the stone or brick floor of a fireplace, often extending out into the room. 2  the fireside as the center of family life. 3  the part of a brick oven, or of a blacksmith's forge, on which the fire rests. 4  Metallurgy the lowest part of a blast furnace, on which the molten metal and slag are deposited.