Which of the following is not an acceptable fastener according to existing standards?

Galvanized nails are generally not considered an acceptable fastener in the context of lightning protection systems according to existing standards. Lightning Protection Systems require fasteners that achieve certain conductivity standards to ensure effective grounding and bonding. Galvanized nails, while resistant to corrosion due to their zinc coating, can introduce materials that do not possess the necessary conductivity required for a proper electrical connection.

In contrast, stainless steel screws, copper rivets, and brass bolts are materials that align more closely with the standards for lightning protection. Stainless steel offers a good combination of strength and corrosion resistance. Copper rivets are excellent conductors, making them ideal for grounding purposes, while brass bolts also provide good conductivity and durability. Recognizing the importance of these materials is crucial for effective lightning protection installation.