The answer to 'why is my smoke detector hot to touch' is that the smoke detector may be malfunctioning or overheating. Smoke detectors contain small electrical components that generate some heat during normal operation, but they should not be hot to the touch. If your smoke detector is unusually hot, it could be a sign of an internal issue or a fire hazard.
Some common causes of a hot smoke detector include a faulty component, a wiring problem, or excessive dust buildup inside the device. In some cases, the smoke detector may be placed too close to a heat source, like a light fixture or heating vent, causing it to overheat. If the detector is hot, you should investigate the issue promptly and consider replacing the unit if the problem persists.