The TMOV is constructed with a conventional MOV ceramic disc and a thermal activated element inside the coating. Sometimes a conventional MOV will be exposed to an energy level that is beyond its capabilities. Sometimes an MOV has reached the end of its useful life. Either of these conditions can result in rapid burning. It is important to disconnect the MOV from the circuit as quickly as possible to lessen the chance of serious damage. TMOV response time is fast because the thermal element is mounted inside the part on the ceramic disc itself. This is still not a 100% solution to MOV destruction, however. This is just another level of insurance against the possibility of physical damage.