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.
Dig the Fire Pit. Mark out how large you want your fire pit to be and start digging a hole. Your fire pit should be about 1 foot deep. I tried just using a shovel for this part, but found that clawing with my hoe and then hoisting out the loose dirt with my shovel worked better.