Fugitive emission compliance per ISO 15848-1 Class AH is mandatory for LNG ball valve stem seals. Live-loaded packing with bellows or dual chevron designs achieves leakage rates below 50 ppm across full thermal cycles from ambient cooldown to cryogenic operation. https://globalsealstech.com/product-category/oil-gas-seals/api-6d-ball-valve-and-lng-seals/