GB/T 2424.27-2013 "Environmental Testing - Supporting Documentation and Guidance - Calculation of Uncertainties in Temperature and Humidity Climatic Chambers" is a supporting document within the environmental testing series. Its core content provides methods and examples for estimating the uncertainty of performance indicators for temperature and humidity test chambers under steady-state conditions (such as constant temperature and humidity). It helps testing personnel understand and quantify the sources of measurement uncertainty for environmental conditions (temperature and humidity) inside the test chamber, and perform combined calculations to scientifically evaluate the reliability and accuracy of environmental test results. This guideline applies to the performance evaluation of various climatic environmental testing equipment (such as temperature chambers, humidity chambers) and even entire testing rooms.