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.
If your fireplace has a sitting-height hearth, it's the ideal spot to soak up the fireplace's warmth or roast marshmallows. A sitting-height hearth also offers extra seating in your room and is a good setting for family photos.f your fireplace has a sitting-height hearth, it's the ideal spot to soak up the fireplace's warmth or roast marshmallows. A sitting-height hearth also offers extra seating in your room and is a good setting for family photos.