GB/T 1038.1-2022 specifies two core test methods for determining the gas permeability of plastic films, sheets, and multilayer structures: the pressure sensor method and the gas chromatography method under differential pressure conditions. The fundamental principle involves separating the test chamber into high- and low-pressure zones using a specimen. By leveraging the gas permeation characteristics driven by the pressure difference, the material's barrier performance against gases is evaluated, providing support for material selection in fields such as packaging and electronics. The test requires the use of a differential pressure gas permeability tester equipped with a permeation cell, pressure sensors, and a vacuum pump. It accurately monitors pressure changes on the low-pressure side, and after data processing, yields gas permeability results, offering a unified technical basis for quality control and performance evaluation of related products.