On Mon, Apr 17, 2017 at 1:33 PM, Tom Metro <tmetro+hhack...@gmail.com> wrote:
> Federico Lucifredi wrote: > > This excess life span I detected in use leads me to think the sensor > > chemistry decays even when warehoused and not in powered use. > > Sure, that makes perfect sense given what we know about the sensors. The > author of the teardown you referenced speculated that the limited > lifespan was due to evaporation of the liquid and accumulation of > contaminants in the activated carbon filter. > > > > I think the lifespan runs from the date of manufacturing, and exceed > > the warranty by an unknown amount... > > Yes, I assumed as much. As with any engineering parameter, the system > should be designed with sufficient margin in excess of what is needed. > And with a life safety device, even greater margins. > > But the issue at hand - with respect to having all your alarms die at > once - is not the actual life of the sensor, but the duration of the EOL > timer. > >From documentation that I found, the EOL timer is activated upon first "power" - so installation by electrician if powered with battery backup, or activation by consumer. In my house, the detectors were all installed during construction of the house. They all died 6 years to the day from the time they were installed.
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