Air Conditioning System or more commonly known as AHU (Air Handling Unit) or VAC (Ventilating and Air Conditioning), plays an important role in various industries. One of the references to the VAC System is the Radioactive Waste Treatment Plant (IPLR), which is a liquid, semi-liquid and solid radioactive waste processing building designed in such a way that it meets the requirements of a nuclear installation and is closed, tight and sturdy. The VAC (Ventilation and Air Conditioning) and exhaust gas (Off-gas) systems have the main function of maintaining the condition of the IPLR room and to achieve optimal operation, it is necessary to minimize various disturbances (trouble) by always carrying out preventive maintenance such as replacing loose v-belts, adding grease, tightening bolts, sheave alignment, measuring motor amperage, system measurement, HEPA filter replacement. Maintenance optimization provides a great opportunity for cost savings and increased equipment life in HVAC systems. The purpose of this study is to determine the preventive maintenance characteristic of VAC system in radioactive waste treatment facility.