Chain should be removed from service if the elongation exceeds ___%.

The correct threshold for when chain should be removed from service is when the elongation exceeds 5%. This percentage indicates that the chain has undergone deformation due to excessive load or wear, which can potentially compromise its strength and integrity.

When a chain stretches beyond this point, it signifies that the material properties may have been altered, leading to a higher risk during use. This is critical in rigging and hoisting applications, where the reliability and safety of lifting operations depend on the chain's ability to perform as designed.

Monitoring elongation is key in maintaining safety standards; exceeding the 5% elongation means that the risk of failure increases significantly, making the chain unfit for further use without proper evaluation and potential replacement.