Final answer:
The NFPA specifies that the minimum distance between the center of a fire hydrant outlet and the finished grade of the ground around the hydrant should be 18 inches.
Step-by-step explanation:
The minimum distance between the center of a fire hydrant outlet and the finished grade of the ground around the hydrant, according to the NFPA (National Fire Protection Association), is typically 18 inches. This measurement ensures that the fire hydrant remains accessible and visible during emergencies.