EricJM

I have an old, hard-wired smoke detector that has a battery backup. The wires to the power are cut, and it does not have a battery, yet in complete darkness, it emits a faint green light. My first inclination was that the detector contained a hidden camera and the light is coming from the IR emitter, however my cell phone camera does not detect any IR. Does anyone have an explanation? Do LED's act as capacitors? This is a 60's or 70's model detector.