Cooling is one of the costly factors in data centers in terms of overall power consumption. Over the past few decades, traditional cooling approaches have maintained the facility's equipment during its operation. However, with the increasing demands of networking and computation, data centers are now facing substantial challenges in saving energy and reducing the power usage effectiveness. Many innovative strategies have been developed to respond to the demands. Several approaches relate to the change in the density of working gas. The locations of data centers are not limited to sea level. For example, the world's highest data center, the ALMA correlator located in the Andes of northern Chile, is more than 5,000 m above the sea level. The air density is only 60% compared with the air density at sea level, which can considerably affect the cooling capabilities because electronics cooling is related to the density of the working gas. Meanwhile, humidity and the types of working gas can affect both fan performance and electronics cooling capabilities. Theoretically, the effect of the density of the working gas on electronics cooling capabilities can be predicted by the ideal gas law, fan laws, and heat convection equations. In this study, we conducted an experimental study on the heat sink performance at a constant volumetric airflow rate under various pressure conditions and verified the effect of the change in the density of the working gas on electronics cooling performance. First, we measured the flow rate of different fan duties via AMCA 210 airflow bench. Second, we used an altitude chamber to simulate the environmental conditions of varying altitude levels. In the altitude chamber, we set up a heat sink and a fan connected serially in a duct. A heat sink was mounted on a dummy heater heated with a constant power of 165 W, and a fan set at constant speed was monitored during the test period. The correlations between CPU case temperature, outlet temperature, pressure drop, and environmental conditions were investigated.