Abstract: The breath alcohol analyzer, or breathalyzer, is essential for measuring breath alcohol content in law enforcement, particularly in drunk driving cases. Operating on two principal mechanisms - fuel cell and infrared absorption - these devices are deployed at various altitudes by traffic control authorities across China. Accurate readings are critical for ensuring rigorous and fair law enforcement. According to China’s National Verification Regulation JJG657-2019 for breath alcohol analyzers, these instruments are tested using first-class national certified reference materials (CRMs C₂H₅OH/Air) or ethanol standard gas. Appendix C indicates that the reference materials’ property values, measured in mg/L, are influenced by atmospheric pressure, necessitating corrections based on the pressure at the usage location. However, the extent to which atmospheric pressure affects the breathalyzer’s accuracy remains understudied. This study investigates the impact of altitude on measurement accuracy for both types of breathalyzers, conducting field verifications at 20 m and 3560 m altitudes. The results show that, for fuel cell type analyzers commonly used by traffic police, the deviation at critical points for determining drunk driving does not exceed 0.04 mg/L. Altitude impacts on these devices fall within a manageable error range, preserving measurement accuracy. Thus, accurate breath alcohol measurement for drunk driving law enforcement remains viable in China’s high-altitude regions.