GB/T 2424.5-2021 "Environmental Testing - Part 3: Supporting Documentation and Guidance - Confirmation of the Performance of Temperature Chambers" replaces the previous edition and is identical to the international standard, providing a performance confirmation scheme for temperature chambers under no-load conditions. It removes the definition of "temperature extreme," simplifies environmental measurement requirements, and adds a chapter on measurement methods. The standard clarifies key indicators such as temperature fluctuation, spatial temperature difference, and temperature gradient, along with measurement rules, specifying the use of 9-point or 15-point sensor placement methods based on the chamber's volume. It applies to routine monitoring scenarios, standardizes testing procedures and data recording requirements, ensures the reliability of temperature test results, and lays the foundation for evaluating the environmental adaptability of products.