Disposable smoke alarms... Why?

esuhl

One of my smoke alarms doesn't work. There's no easy way to open it, and it's marked "Battery not replaceable" and "Replace by May 2018" (what a coincidence!). Apparently it was designed to last ten years and be thrown away.

So, I cracked it open and there are three (apparently flat) lithium CR123A 3V cells. Presumably I could recharge these in an appropriate charger. So... why is it disposable...? It seems such a waste!

Is it because the radioactive substance has decayed so much in ten years that the sensitivity of the alarm is unsafe?

Do alarms with replaceable batteries also have to be thrown away after ten years?

As a safety product, of course I will buy a new smoke alarm to replace the old one. I'm just curious...

Gloomendoom

The sensor degrades and becomes unreliable after ten years. There is no point in replacing the batteries. Sealing the case helps to prevent people trying.

Note that not all batteries with lithium in their name are rechargeable. The type used in smoke alarms are not.

Nilrem

Gloomendo has it spot on.

The sensors in many devices, especially those related to safety have very precise tolerances they have to work within, smoke alarms and carbon monoxide alarms tend to use sensors that degrade/drift out of tolerance after X years (varies a bit depending on sensor type, IIRC it tends to b e 8-10 years after manufacture).
As the sensor is built into the main board and non replaceable the whole unit has to be thrown away, it's a bit of a waste but not much given it's every 8-10 years (consider that many people will get through 5+ much more complex mobile phones in that period each of which generates a lot more waste).

We use units with replaceable batteries (and keep batteries spare;)), and I long ago got into the habit of writing the "replacement" date on the underside of the units in red marker when I fit them for us or friends, as although there is always a note somewhere it's often on a little sticker and not obvious unless you know to look for it.

Robisere

Ours are mains-wired and I test them once a month with a broom handle.

Lorian

Robisere wrote: »

Ours are mains-wired and I test them once a month with a broom handle.

And did you check the expiry date - they too normally have a 10 year life. There is usually a sticker on them with the date.

grumpycrab

Lorian wrote: »

And did you check the expiry date - they too normally have a 10 year life. There is usually a sticker on them with the date.

Oops! Ours have been going 20 years+. Better check them fast.

SnowTiger

Robisere wrote: »

Ours are mains-wired and I test them once a month with a broom handle.

Useful to know it can detect a broom handle.

Can it detect smoke?

I guess you could set fire to the broom handle and see what happens. :rotfl:

Neil_Jones

Why do you need a broom handle? Don't most main-wired smoke alarms have buttons or switches on a control panel at a more accessible height?

pmartin86

SnowTiger wrote: »

Useful to know it can detect a broom handle.

Can it detect smoke?

I guess you could set fire to the broom handle and see what happens. :rotfl:

Could? You mean there'r another way???? So many wasted brooms...

EssexExile

Neil_Jones wrote: »

Why do you need a broom handle? Don't most main-wired smoke alarms have buttons or switches on a control panel at a more accessible height?

What control panel?
They're just smoke detectors screwed to the ceiling. I'm 6'2" so I don't need a broom handle & the wife checks their "real smoke" detection capabilities with her cooking now & again.

custardy

Neil_Jones wrote: »

Why do you need a broom handle? Don't most main-wired smoke alarms have buttons or switches on a control panel at a more accessible height?

EssexExile wrote: »

What control panel?
They're just smoke detectors screwed to the ceiling. I'm 6'2" so I don't need a broom handle & the wife checks their "real smoke" detection capabilities with her cooking now & again.

Same here. Just like standard smoke alarms but with a mains feed & battery back up.