The application of environmentally friendly refrigerants to air-conditioning systems is receiving considerable research attention; however

the flammability of the refrigerants cannot be ignored. Leaks represent a significant potential safety hazard. In this study fault tree analysis is used to establish a split air-conditioning system leakage model using statistical data from an air-conditioning manufacturer with a high market share. A qualitative and quantitative analysis of the causes of leakage and the components involved

is conducted. The results show that the probability of leakage on the outdoor side of the split air-conditioning system is approximately 2.72×10-3

which is higher than the probability of 2.74×10-4 on the indoor side. The most likely components to become a source of leakage by descending probability on the outdoor side are the outdoor pipe connection bell mouth

condenser

four-way valve

and two-way valve. In contrast

on the indoor side the most likely components to become a source of leakage by descending probability are the evaporator piping

evaporator elbow

evaporator inlet

and outlet connecting pipe. The causes of system leakage by descending probability are process defects

improper brazing

improper operation

and fatigue cracks. This study provides data support for the in-depth study of the selection of leak-prone points for split air-conditioning systems and provides comprehensive guidance for leakage prevention.