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Discussion Starter · #1 ·
Dear experts,

We just purchased our new old house, and installed hard-wired smoke detectors. The wiring was already there. After some short time, they all started making alarm sound. There was nobody at home, so our neighbors called the fire department. Fortunately, I arrived at the same time as they. I have a question, why this happened?
 

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If they are interconnected by the hardwire, one sounding makes them all sound. Some have the indicator light stay on in alarm so you know which one alarmed. No one home means no cooking or showering going on. Do you know which one initiated the alarm? Is one close to an HVAC vent?
 
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Discussion Starter · #3 ·
If they are interconnected by the hardwire, one sounding makes them all sound. Some have the indicator light stay on in alarm so you know which one alarmed. No one home means no cooking or showering going on. Do you know which one initiated the alarm? Is one close to an HVAC vent?
Thank you very much for your answer. At that time I did not pay attention which one started the trouble. I will try to do it when I get there again.
We do not have any HVAC vent blowing, as the house is heated by baseboard radiators.
 

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That is unusual with new detectors. If it happens again and you can determine which one, and no known cause can be found, it could be defective. Are they ionization or photoelectric?
Hardwired are powered by the black and white wires. Typically there is also a red or orange wire that interconnects them. If interconnected, they all sound.
Make sure fin tubes in the baseboard heaters are clean. A little bit of burning dust can alarm a sensitive detector without visible smoke. Just a thought.
 
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Sometimes it's just a bad smoke alarm. Happened to me in the middle of the night with a 6 month old smoke.
Ran around and nothing, no smoke, no smells. Kidde replaced it for free with just a phone call.
 

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some models newer kidde alarms have a lot of problems with false trips.
 
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Thank you! I did not realize their life is so short.
As electronic components age, they can change values causing the circuit not to work properly. Not what you want with a life safety device.

Every watch a TV that's 10 years old? And it's unlikely a TV will save your life.
 
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My new old house is 102 years old :)
Many of the homes I work in are that old. Both of my parents homes are that old.

As someone else mentioned already, the replacement is because it's a life safety device.

Your life is worth more than replacing a smoke detector (or 20).

Sent from my new phone. Autocorrect may have changed stuff.
 

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Yesterday I came there again, and one of the detectors that I had unplugged previously, but forgot to remove the battery, was making alarm noise again. And yes, that is Kidde!
That's not the style that has problems.

Probably just dirty and needs to be blown out.

The manufacturers say to replace every 10 years but they can work much longer than that - just need to test regularly, preferably with real smoke from incense or something.

I suspect it has to do with creating an ongoing market.

Funny thing is, the new ones with sealed backup batteries are complete junk and get disabled due to false trips, so the older ones can actually be more safe.

reviews: https://www.amazon.ca/Kidde-P4010AC...dwired&qid=1582787517&sr=8-14#customerReviews
 
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Also something to keep in mind.


Some brands/models of hardwired smoke detectors don't play well with other brands/models. May cause false alarms.


Best to stick with all one brand and model.



This is what I did with my home. Don't plan on being here much longer but I installed wireless interconnected smoke detectors. Can't afford to buy all the ones I need at one time so i buy one per month but always buy the exact same brand and model.
 

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That's not the style that has problems.



Probably just dirty and needs to be blown out.



The manufacturers say to replace every 10 years but they can work much longer than that - just need to test regularly, preferably with real smoke from incense or something.



I suspect it has to do with creating an ongoing market.



Funny thing is, the new ones with sealed backup batteries are complete junk and get disabled due to false trips, so the older ones can actually be more safe.



reviews: https://www.amazon.ca/Kidde-P4010AC...dwired&qid=1582787517&sr=8-14#customerReviews
Smoke detectors are reccomend to be replaced every 10 years, this is why they have an expiry date. The reason they need to be replaced is because the sensors eventually degrade in quality to the point where they’re no longer effective.

Some smoke detectors (ionization type) also contain radioactive material (americium-241, a radioactive isotope). I suspect that these smoke detectors expire due to the half life of the radioactive isotope, but I can't find any evidence of that.

Sent from my new phone. Autocorrect may have changed stuff.
 

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Smoke detectors are reccomend to be replaced every 10 years, this is why they have an expiry date. The reason they need to be replaced is because the sensors eventually degrade in quality to the point where they’re no longer effective.

Some smoke detectors (ionization type) also contain radioactive material (americium-241, a radioactive isotope). I suspect that these smoke detectors expire due to the half life of the radioactive isotope, but I can't find any evidence of that.

Sent from my new phone. Autocorrect may have changed stuff.
Carbon monoxide sensors do indeed degrade and become inaccurate.

Smoke, not so much.

americium-241 has a half life of over 400 years. (http://large.stanford.edu/courses/2011/ph241/eason1/)

Should be okay for far more than 10 years.

The weaker the radioactive source, the lower the alarm threshold so that even if you were right and it degraded much faster, you would get more false alarms, not a failure to alarm.

The main issue with ionization is that the sensor gets dirty - internal dirt actually reduces current flow so can get false trips.

Photo-electric uses an LED and samples the sensor -> ie the led is not on that much, can last a very long time. Possible for sensing part that detects scattered light to go bad but again 10 years isn't that long.

Again - the main problem is dust, regardless of type -> can throw off sensing thresholds and block the vents on the sensing chamber.

With proper maintenance (cleaning) and testing, there's no real reason why an alarm needs to be replaced after only 10 years.

People who don't touch the alarms - don't bother to test, vacuum/blow out the alarm should probably replace every 10 years.
 
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