A pressure relief mechanism includes: a pedestal, a cover assembly, and a position limiter. An exhaust port is provided on the pedestal. The cover assembly is configured to close or open the exhaust port. The position limiter is snap-fastened to the cover assembly. The position limiter includes a first elastomer and a first limiting portion. The first limiting portion is configured to: when the cover assembly closes the exhaust port, restrict the position limiter from moving relative to the pedestal; and when a pressure in the box increases, make the position limiter move along an opening direction of the cover assembly to free the first limiting portion from constraint of the pedestal and enable the position limiter to rotate relative to the cover assembly under resilience of the first elastomer.