This standard specifies a free-falling dart impact test method for determining the impact resistance of plastic films and sheets using the "staircase method" (also known as the "up-and-down method"). The core principle involves a dart with a hemispherical head falling freely from a fixed height to impact a horizontally clamped specimen. Based on whether the specimen ruptures, the "staircase method" is used to statistically calculate the precise impact energy (or mass) required for 50% failure, thereby characterizing the material's impact strength. Implementing this method requires a free-falling dart impact tester, which primarily consists of a release mechanism, a vertical guide tube, a dart head, and a clamping system, and is sometimes referred to as a dart impact tester.