This John C. Stennis Space Center (SSC) standard (SSTD) outlines the allowable leakage for existing gas distribution systems at SSC. It defines the leakage which is acceptable and those which require repair. Allowable leakage for new systems is covered under existing standards.
Systems and software engineering — Systems and software product Quality Requirements and Evaluation (SQuaRE) — Common Industry Format (CIF) for usability: General framework for usability-related information (ISO/IEC TR 25060:2010)