The answer to 'why is my smoke detector hot to touch' is that the smoke detector may be overheating due to an electrical issue or a malfunctioning component. This can be a sign of a serious problem that requires prompt attention.
Common causes include a short circuit, a faulty power supply, or a problem with the internal circuitry. The heat could also be a result of the smoke detector being placed too close to a heat source, such as a light fixture or heater. In some cases, the smoke detector may simply be old and need to be replaced.