This technical brief deconstructs the ASTM D2000 classification system, providing a deep dive into elastomer chemistry for industrial applications. It focuses on the mechanical behavior of EPDM, NBR, and FKM under high-pressure environments ($N/mm^2$). By analyzing critical performance data—such as Compression Set percentages and Shore A Hardness—the guide offers a diagnostic framework for preventing common failure modes like Explosive Decompression (ED) and Chemical Swell, aligning material selection with 2026 industrial reliability standards.