I'm having a hard time understanding a requirement to replace smoke detectors every 10 years (or whatever the manufacturer suggests). With previous generations of ionization based detectors, I understand that the radioactive substance would decay over time, reducing its ability to reliably do what it's supposed to do, but the photoelectic ones I'm having a harder time understanding exactly why there is still a requirement to replace them.
For example, I own 2 Nest Protect 2nd generation smoke/CO detectors, which as I understand use a split-spectrum photoelectric sensor. The device will trigger all kinds of alerts and warnings when it comes time to replace them. However, as this is LED based, why does it do this? Is there an actual technical reason for replacing it, or does this basically come down to some law somewhere?
Best Answer
It likely has to do with the lifetime of the hardware itself. Remember, there's a circuit board and a light source, as well as a detector. Those don't last forever. So the manufacturer certifies the device will work for only 10 years, and then (in some modern units) sets a hard sunset by using an unreplacable battery.
In some regards, this solves the problem of people just putting new batteries into older detectors forever, not realizing the devices have stopped working (when was the last time you tested one?)