Sour service (H2S) dramatically accelerates RGD damage by embrittling elastomers. NACE TM0187 and TM0296 testing evaluates volume swell and hardness change in H2S environments. Only low-swell, high-ACN HNBR and specific FFKM grades maintain RGD resistance in sour HPHT wells containing 20% H2S and 30% CO₂ at 200°C https://globalsealstech.com/oil-gas-seals/