GB/T 12085.8-2022 specifies reliability test methods for optical and photonic instruments and their components under three severe pressure conditions: high internal pressure, low internal pressure, and immersion. This standard aims to simulate the sealing performance and tolerance of products under abnormal air pressure or direct contact with liquids in special scenarios such as aircraft cabin takeoff and landing, deep-water operations, and submarines. Among them, high internal pressure and low internal pressure tests typically require the use of a pressure test chamber (low-pressure environmental test chamber) to simulate pressure changes, while immersion tests require the use of a water immersion (waterproof) test chamber capable of controlling water temperature and depth. This set of methods serves as a critical basis for evaluating the environmental adaptability of precision optical instruments such as periscopes, aerospace cameras, and underwater observation equipment.