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  • FIRST POST
    • esuhl
    • By esuhl 5th May 18, 3:31 AM
    • 8,250Posts
    • 6,045Thanks
    esuhl
    Disposable smoke alarms... Why?
    • #1
    • 5th May 18, 3:31 AM
    Disposable smoke alarms... Why? 5th May 18 at 3:31 AM
    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...
Page 1
    • Gloomendoom
    • By Gloomendoom 5th May 18, 4:23 AM
    • 14,387 Posts
    • 19,246 Thanks
    Gloomendoom
    • #2
    • 5th May 18, 4:23 AM
    • #2
    • 5th May 18, 4:23 AM
    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.
    Never argue with stupid people, they will drag you down to their level and then beat you with experience. - Mark Twain
    • Nilrem
    • By Nilrem 5th May 18, 5:02 PM
    • 2,390 Posts
    • 1,567 Thanks
    Nilrem
    • #3
    • 5th May 18, 5:02 PM
    • #3
    • 5th May 18, 5:02 PM
    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
    • By Robisere 6th May 18, 8:57 PM
    • 2,305 Posts
    • 3,110 Thanks
    Robisere
    • #4
    • 6th May 18, 8:57 PM
    • #4
    • 6th May 18, 8:57 PM
    Ours are mains-wired and I test them once a month with a broom handle.
    I think this job really needs
    a much bigger hammer.
    • Lorian
    • By Lorian 6th May 18, 9:23 PM
    • 4,406 Posts
    • 2,519 Thanks
    Lorian
    • #5
    • 6th May 18, 9:23 PM
    • #5
    • 6th May 18, 9:23 PM
    Ours are mains-wired and I test them once a month with a broom handle.
    Originally posted by Robisere
    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
    • By grumpycrab 6th May 18, 10:18 PM
    • 3,598 Posts
    • 1,634 Thanks
    grumpycrab
    • #6
    • 6th May 18, 10:18 PM
    • #6
    • 6th May 18, 10:18 PM
    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.
    Originally posted by Lorian
    Oops! Ours have been going 20 years+. Better check them fast.
    If you put your general location in your Profile, somebody here may be able to come and help you.
    • SnowTiger
    • By SnowTiger 6th May 18, 10:30 PM
    • 3,315 Posts
    • 2,301 Thanks
    SnowTiger
    • #7
    • 6th May 18, 10:30 PM
    • #7
    • 6th May 18, 10:30 PM
    Ours are mains-wired and I test them once a month with a broom handle.
    Originally posted by Robisere
    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.
    • Neil Jones
    • By Neil Jones 6th May 18, 11:02 PM
    • 1,378 Posts
    • 835 Thanks
    Neil Jones
    • #8
    • 6th May 18, 11:02 PM
    • #8
    • 6th May 18, 11:02 PM
    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
    • By pmartin86 6th May 18, 11:26 PM
    • 529 Posts
    • 325 Thanks
    pmartin86
    • #9
    • 6th May 18, 11:26 PM
    • #9
    • 6th May 18, 11:26 PM
    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.
    Originally posted by SnowTiger
    Could? You mean there'r another way???? So many wasted brooms...
    • EssexExile
    • By EssexExile 7th May 18, 10:38 AM
    • 2,925 Posts
    • 2,034 Thanks
    EssexExile
    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?
    Originally posted by Neil Jones
    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.
    Tall, dark & handsome. Well two out of three ain't bad.
    • custardy
    • By custardy 8th May 18, 6:44 PM
    • 33,671 Posts
    • 28,586 Thanks
    custardy
    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?
    Originally posted by Neil Jones
    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.
    Originally posted by EssexExile
    Same here. Just like standard smoke alarms but with a mains feed & battery back up.
    • PasturesNew
    • By PasturesNew 8th May 18, 6:46 PM
    • 63,211 Posts
    • 370,196 Thanks
    PasturesNew

    So, I cracked it open ....
    Originally posted by esuhl
    Sealing the case helps to prevent people trying.
    Originally posted by Gloomendoom
    Obviously not
    • Robisere
    • By Robisere 8th May 18, 7:22 PM
    • 2,305 Posts
    • 3,110 Thanks
    Robisere
    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.
    Originally posted by Lorian
    Landlord keeps a record and sends people round to check, along with Gas Safety and Fire Checks. I live in Sheltered Accomodation.

    Last changed 5 years ago, but thanks for the information.
    I think this job really needs
    a much bigger hammer.
    • joeypesci
    • By joeypesci 9th May 18, 12:22 AM
    • 508 Posts
    • 184 Thanks
    joeypesci
    Seen people come into our office every year with a broom and a hood on the end. Turns out that covers the alarm and releases a bit of smoke to see if the sensor is still working. Quite interesting.
    • Blackbeard of Perranporth
    • By Blackbeard of Perranporth 9th May 18, 12:35 PM
    • 5,190 Posts
    • 31,163 Thanks
    Blackbeard of Perranporth
    The sensor lasts around 10 years, replace!
    Commemorate Celebrate Inspire
    #RAF100 A century of service!
    • peachyprice
    • By peachyprice 9th May 18, 3:05 PM
    • 19,494 Posts
    • 45,199 Thanks
    peachyprice

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

    Do alarms with replaceable batteries also have to be thrown away after ten years? And yes
    Originally posted by esuhl
    .....................
    Accept your past without regret, handle your present with confidence and face your future without fear
    • peachyprice
    • By peachyprice 9th May 18, 3:08 PM
    • 19,494 Posts
    • 45,199 Thanks
    peachyprice
    Oops! Ours have been going 20 years+. Better check them fast.
    Originally posted by grumpycrab
    I didn't realise they expired until we bought a new 'toast safe' one, when we took the old one down it had an expiry date on it.
    Accept your past without regret, handle your present with confidence and face your future without fear
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