The flash point and the AIT(auto-ignition temperature) are the most important combustible properties used to determine the potential for the fire and explosion hazards of flammable material. In order to know the accuracy of data in MSDS(Material Safety Data Sheet), the flash point of n-acids were measured by using Pensky-Martens closed cup tester(ASTM D93), Setaflash closed cup tester(ASTM D3278), Tag open cup tester(ASTM D1310) and Cleveland open cup tester(ASTM D92). Also, the AIT of n-acids were measured by using ASTM E659-78 tester. The measured the flash points and the AIT were compared with literatures and MSDS in KOSHA. The measured the flash points and the AIT were different from those in literatures and MSDS. Therefore, This paper shows that it is needed to investigate the MSDS compatibility of n-acids for the fire safety objectives.