GB/T 2424.6-2021 "Environmental Testing—Part 3: Supporting Documentation and Guidance—Confirmation of the Performance of Temperature/Humidity Chambers" is identical to the international standard and specifies methods for confirming the performance of temperature/humidity chambers under no-load conditions. It introduces the new term "spatial relative humidity difference," revises the definition of humidity gradient, and expands content on test environments and load requirements. The standard clearly defines sensor placement specifications, adopting a 9-point or 15-point layout based on the chamber volume, and specifies four recommended methods for humidity measurement along with accuracy requirements. It is applicable for the regular performance monitoring of test chambers, ensuring the accuracy and comparability of environmental test data, and supports reliability testing of products in fields such as electronics and aerospace.