What is the maximum interval for placing air terminals that extend 24 inches or more above the object to be protected?

The maximum interval for placing air terminals that extend 24 inches or more above the object being protected is established based on industry standards for effective lightning protection. Air terminals, commonly known as lightning rods, are critical components in a lightning protection system as they intercept lightning strikes and direct the electrical energy safely to the ground.

When the air terminals extend significantly above a structure (24 inches or more), the recommended placement interval is set at a maximum of 25 feet. This distance ensures that the air terminals can sufficiently provide protection to the area beneath them from lightning strikes, effectively minimizing the risk of lightning-induced damage. The standard is designed to create an effective zone of protection, reducing the likelihood of direct strikes to the protected structure.

Other intervals mentioned, such as 15, 20, and 30 feet, do not align with the recognized guidelines for the placement of air terminals of this height. The 25-foot maximum ensures a balance between adequate protection and practical installation for maintaining a lightning protection system's effectiveness.