What is the maximum spacing allowed for an Extra Hazard hydraulically calculated system with a density less than 0.25 gpm/ft²?

For an Extra Hazard hydraulically calculated system, maximum spacing requirements are essential for ensuring adequate fire protection. When the density of the system is less than 0.25 gpm/ft², the maximum spacing allowed between sprinklers is indeed set at 15 feet. This is established by fire safety codes and standards which aim to provide sufficient overlapping coverage from the sprinklers' spray patterns to handle the higher fire risk associated with Extra Hazard classifications.

This specific spacing ensures that even in areas where the water density may be lower, the sprinklers can still adequately protect the area by providing sufficient water distribution to suppress potential fires. It plays a critical role in achieving the right balance between coverage and the operational effectiveness of the fire protection system.