A hearth extension must extend at least how many inches in front of the fireplace opening if it is at least 6 square feet?

A hearth extension that serves a fireplace must provide adequate safety measures to prevent the potential spread of fire. When the fireplace opening is at least 6 square feet in area, the standard requirement dictates that the hearth extension must extend at least 20 inches in front of the fireplace. This is to ensure that any embers or ashes that may fall from the fire are caught by the hearth extension, thereby reducing the risk of fire hazards in the surrounding area. This specific measurement is in line with various building codes that aim to enhance safety in residential fire installations. The other options do not meet the specific requirements outlined for a fireplace of this size, making 20 inches the appropriate answer.