GB/T 18380.33 - 2022 stipulates the vertical spread test of Class A flame for vertically installed bundles of Wires and cables. This standard explains the test principle, specifies the technical requirements for combustion devices and flame characteristics required for Class A testing, and details the selection and installation specifications of the samples. Strictly standardize the test process, covering ignition operation, combustion time control and observation records of flame spread. With this standard, it can accurately evaluate the vertical combustion spread of bundles of Wires and cables under Class A flame conditions, providing a unified detection basis for cable production, power generation and other industries, and helping to improve the safety of cables in fires.