Refers to boilers, pressure vessels (including gas cylinders), pressure pipes, elevators, lifting machinery, passenger ropeways and large-scale amusement facilities that involve life safety and great danger.
According to this definition, air compressors, hydrogen compressors and other types of compressors belong to general machinery.
However, its auxiliary equipment, including gas storage tanks (pressure vessels) and pressure pipelines, are all special equipment.
Safety valve belongs to the safety accessories of special equipment.