The researchers studied how mining a protective coal seam affects gas pressure in China. They measured gas pressure in a test mine to understand how the protected seam changes. As the protective seam was mined, the roof and surrounding rock became looser and more fractured, making it easier for gas to escape. This led to a decrease in gas pressure in the protected coal seam. The study shows that mining a protective seam can significantly impact gas emissions in the main coal seam, reducing gas pressure in the protected area.