CSA N299 Level 1 — Safety-critical N299_L1 1 40 safety_critical Highest level of the CSA N299 quality assurance program. Applies to safety-critical items whose failure could directly affect nuclear safety. Requires the most rigorous supplier QA program, traceability, and records retention (typically life-of-plant, 40 years or more). CSA N299 Level 2 — Safety-related N299_L2 2 25 safety_related Applies to safety-related items that support safety-critical functions. Requires a documented QA program aligned to CSA N299.2, full traceability, and long-term records retention. CSA N299 Level 3 — Important to safety N299_L3 3 15 important_to_safety Applies to items important to safety but not themselves safety-critical or safety-related. Requires a documented QA program aligned to CSA N299.3 with moderate records retention. CSA N299 Level 4 — Commercial grade N299_L4 4 7 commercial_grade Lowest level of the CSA N299 program. Applies to commercial grade items procured for nuclear use without safety implications. Standard commercial QA records retention applies.