GB/T 21782.4-2025 "Powder coatings - Part 4: Calculation of the lower explosion limit" was released in October 2025 and will be implemented in February 2026, replacing the previous version. It applies to the determination and calculation of the lower explosion limit of powder coatings. The standard establishes the principles for relevant determination and calculation, specifies requirements for sampling, acquisition of total calorific value, calculation of the lower explosion limit, and test reports. Calculations can be based on either the total calorific value or the calorific value of combustible components. Compared to the previous version, this update includes revised terminology definitions, improved testing methods, enhanced safety measures, and refined data processing guidelines. Its scope has been expanded to cover new or special-purpose powder materials, providing comprehensive specifications for evaluating the safety performance of powder coatings.