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Old July 31st 20, 01:57 AM posted to alt.home.repair
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trader_4 wrote in
:

On Thursday, July 30, 2020 at 1:43:19 PM UTC-4, Mercellus Bohren
wrote:
do they ever need to be completely replaced?


That would depend on what it actually is. Smoke detectors are
supposed to be replaced at least every ten years. Some of the new
ones have a lifetime battery in them now.


The reason for replacing the whole detecter every so many years is that
most, if not all, can get dirty and become less efficient at detecting
smoke and other particles over time.

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Old July 31st 20, 07:34 AM posted to alt.home.repair
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In alt.home.repair, on Thu, 30 Jul 2020 19:09:26 -0500, dpb
wrote:

On 7/30/2020 6:42 PM, Gil wrote:
On 7/30/2020 1:49 PM, Fred McKenzie wrote:
In article ,
* Mercellus Bohren wrote:

do they ever need to be completely replaced?

The fire alarm people say yes.* Apparently there is some radioactive
material involved, that deteriorates over several years.

Fred

*Ionization smoke alarms* require replacement every ten years. As
mentioned by Fred, the radioactive particle in them deteriorates to the
point where the alarm function becomes very slow to activate. Follow the
manufacturers advice. They're not that costly to begin with if you
spread it out over the ten year life. Cheap insurance.


Yes, you should have at least one of each kind and get new ones
according to the recommended schedule.

Whatever it is that is the basis for a 10-yr replacement period for
ionization smoke detectors, it doesn't seem likely to be owing to the
decay of the isotope. Am-241 has a half-life of 432.2 yrs.


But I wouldn 't necessarily get rid of the old ones. The one that came
with my house, is AC powered and mounted to the upstairs hall ceiling,
is 41 years old and still works, works well I think.

In addition to keeping it this long, I did another no-no. I opened it
up and across the buzzer I put a relay that closes the circuit to a
wire-pair that goes to the Fire input of my burglar alarm. So when the
smoke alarm goes off it notifies the monitoring company.

This was really bad for a while when I made hamburgers in a skillet at
the highest temperature and if I didn't turn off the burner when I
removed the food, it set off the 18 volt siren outside my house (a
couple times at 11PM) and the monitoring company called to see if there
was a fire. (No fire engines yet.)

But by cooking the food two big "notches" less than the hottest, at
about 80%, it no longer sets off the smoke alarm and all is good again.

t_half=432.2;
lambda=log(2)/t_half;
exp(-lambda*t_half) % make sure no typos, etc., ...

ans =
0.5000
exp(-lambda*10) % after 10 years

ans =
0.9841


has only lost 2% of initial activity. That wouldn't seem enough of a
sensitivity loss to me.


Me neither.

I looked at a NFPA study that referenced a Dallas project that tracked
new installations for a period of 10 years that claimed only 27% were
still operational after that time.

However, it did not provide comprehensive data on the causes of the
failures other than most were simply not replacing batteries or taken
down when renters moved or otherwise destroyed. An apparent other
failure mode of significance had to do with not cleaning -- I suppose if
were in kitchen or the like grease buildup and all could do it, but
again it didn't explain what needed cleaning or what the source of not
being clean was.

But source decay wasn't listed at all and if it were the problem, none
would be operational as all would decay at the same rate and have same
relative source strength (presuming the initial population all of same
vintage).


Very interesting. Not surprised.
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Old July 31st 20, 07:53 AM posted to alt.home.repair
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On Thursday, July 30, 2020 at 6:19:24 PM UTC-4, Fred McKenzie wrote:
In article ,
wrote:

On Thu, 30 Jul 2020 13:49:47 -0400, Fred McKenzie
wrote:

In article ,
Mercellus Bohren wrote:

do they ever need to be completely replaced?

The fire alarm people say yes. Apparently there is some radioactive
material involved, that deteriorates over several years.

Fred



That would be smoke detectors ..
Fire Alarms are the break-glass-pull-down thingies.

John-

You got me! I have smoke detectors here, but they give off an alarm.

I wonder which Mercellus meant?

Fred


I meant smoke detectors, not fire alarms. I have a couple of smoke detectors and a couple of combo carbon dioxide/smoke detectors and they both started beeping. The two carbon dioxide/smoke detectors are wired together and to power on one circuit. The started beeping and I replaced the backup batteries. Turns out, both of the CO2/smoke detectors had to be replaced, after about 7 years.
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Old July 31st 20, 09:28 PM posted to alt.home.repair
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On Thu, 30 Jul 2020 23:53:00 -0700 (PDT), Mercellus Bohren posted for all of us
to digest...


On Thursday, July 30, 2020 at 6:19:24 PM UTC-4, Fred McKenzie wrote:
In article ,
wrote:

On Thu, 30 Jul 2020 13:49:47 -0400, Fred McKenzie
wrote:

In article ,
Mercellus Bohren wrote:

do they ever need to be completely replaced?

The fire alarm people say yes. Apparently there is some radioactive
material involved, that deteriorates over several years.

Fred


That would be smoke detectors ..
Fire Alarms are the break-glass-pull-down thingies.

John-

You got me! I have smoke detectors here, but they give off an alarm.

I wonder which Mercellus meant?

Fred


I meant smoke detectors, not fire alarms. I have a couple of smoke detectors and a couple of combo carbon dioxide/smoke detectors and they both started beeping. The two carbon dioxide/smoke detectors are wired together and to power on one circuit. The started beeping and I replaced the backup batteries. Turns out, both of the CO2/smoke detectors had to be replaced, after about 7 years.


That is correct they must be replaced according to the manufacturers specs. The
sensors inside have a finite lifetime.

--
Tekkie
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Old July 31st 20, 09:47 PM posted to alt.home.repair
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On 7/31/2020 3:28 PM, Tekkie´┐Ż wrote:
On Thu, 30 Jul 2020 23:53:00 -0700 (PDT), Mercellus Bohren posted for all of us
to digest...

....

I meant smoke detectors, not fire alarms. I have a couple of smoke detectors and a couple of combo carbon dioxide/smoke detectors and they both started beeping. The two carbon dioxide/smoke detectors are wired together and to power on one circuit. The started beeping and I replaced the backup batteries. Turns out, both of the CO2/smoke detectors had to be replaced, after about 7 years.


That is correct they must be replaced according to the manufacturers specs. The
sensors inside have a finite lifetime.


Looking at current spec sheets it seems more are related to the use of
"tamper-proof" (and hence non-replaceable by design) batteries w/ a
10-yr life.

I've still not found anything that indicates what, specifically is the
failure mode of the device that would otherwise require replacement at
10 year, whether ionization or photoelectric type.

I did discover that apparently a lot of places have now decreed that
ionization-type are not approved as standalone; only in conjunction with
photoelectric type are they allowed by Code in those locales.

--






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Old July 31st 20, 11:33 PM posted to alt.home.repair
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Default FIRE ALARMS

On 7/31/2020 4:28 PM, Tekkie´┐Ż wrote:

On Thu, 30 Jul 2020 23:53:00 -0700 (PDT), Mercellus Bohren posted for all of us
to digest...


On Thursday, July 30, 2020 at 6:19:24 PM UTC-4, Fred McKenzie wrote:
In article ,
wrote:

On Thu, 30 Jul 2020 13:49:47 -0400, Fred McKenzie
wrote:

In article ,
Mercellus Bohren wrote:

do they ever need to be completely replaced?

The fire alarm people say yes. Apparently there is some radioactive
material involved, that deteriorates over several years.

Fred


That would be smoke detectors ..
Fire Alarms are the break-glass-pull-down thingies.
John-

You got me! I have smoke detectors here, but they give off an alarm.

I wonder which Mercellus meant?

Fred


I meant smoke detectors, not fire alarms. I have a couple of smoke detectors and a couple of combo carbon dioxide/smoke detectors and they both started beeping. The two carbon dioxide/smoke detectors are wired together and to power on one circuit. The started beeping and I replaced the backup batteries. Turns out, both of the CO2/smoke detectors had to be replaced, after about 7 years.


That is correct they must be replaced according to the manufacturers specs. The
sensors inside have a finite lifetime.


I suspect he meant carbon monoxide detector. These do have a finite
lifetime.


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