UV-C disinfection equipment must prevent irradiation whenever a person is present, but low-cost interlocks based on a single sensor can miss stationary occupants or respond to targets outside the intended detection boundary. This study presents a low-cost infrared-microwave dual-mode human-presence detection and safety-prioritized interlock method for UV-LED disinfection lamps. A passive infrared (PIR) sensor provides rapid sensitivity to human motion, whereas a 24 GHz microwave radar provides complementary sensitivity to stationary occupants and micro-motion. The conditioned digital sensor outputs are fused using a conservative OR rule. Any presence indication, emergency-stop event, or diagnosed safety fault deasserts the UV-enable signal locally. Reactivation is permitted only after both sensors continuously report no presence for a 2 s confirmation interval and a valid operating request remains active. A hierarchical state machine separates the safety state from AUTO, MANUAL, and STOP operating modes, ensuring that no operating command can bypass the local presence interlock. Prototype experiments evaluated intrusion shutdown, stationary-person detection, short-range and breath-holding limitations, and out-of-zone radar triggering. In both AUTO and MANUAL modes, the UV-enable signal was deasserted within the prototype design target of 200 ms after intrusion. Repeated sampling within a finite observation window increased the measured probability of detecting stationary occupants under normal respiration. The tested modalities showed complementary behavior: radar mitigated the limited sensitivity of PIR to stationary occupants, whereas PIR retained useful sensitivity during entry, postural changes, and some close-range conditions. Radar triggering through thin partitions remained a major availability limitation when the electromagnetic sensing region extended beyond the intended UV hazard zone.