Full Description The standard applies to pilot operated and direct acting pressure reducing, pressure relieving (back pressure), differential pressure and temperature regulators. The FCI has periodically updated the standard since the standard\'s development in 2001. Responding to the industry\'s request, the FCI has recently updated the standard to include Class VIII, which is a \"no permissible leakage\" or \"bubble tight\" standard generally associated with resilient seating regulators either balanced or unbalanced with \"O\" rings or other gapless seals.