What are 4 hour fusible links typically made of?

• A. Copper wires
• B. Plastic straps
• C. Wooden wedges or metal hooks
• D. Glass beads

Answer: (C)

Fusible links rated for four hours rely on a simple, heat-activated mechanical hold rather than electrical components. They’re designed to fail or release when exposed to fire conditions, helping the assembly maintain its rating. Wooden wedges or metal hooks are typical because they respond predictably to heat: wood can burn away and metal hooks can weaken or detach, allowing the mechanism to release at the right time. Copper wires, plastic straps, and glass beads aren’t used for this purpose because they don’t provide the same reliable, purely mechanical release under fire exposure.