GB/T 20969.4-2021 "Special environmental conditions plateau machinery, Part 4: Guidelines for testing on plateau natural environment, internal combustion powered machinery" specifies the guiding principles for testing internal combustion powered machinery in plateau natural environment at altitudes of 2000 meters to 5000 meters. This standard applies to internal combustion powered machinery in Engineering machinery and aims to evaluate its performance and Reliability in plateau environment. The standard details the test methods and requirements to ensure that the machinery can operate properly and maintain Stability in plateau areas. Tests on Power, Fuel Consumption, Exhaust Pollutants, etc. are included to ensure the adaptability of internal combustion machinery in special environments.