Go Back  PPRuNe Forums > PPRuNe Social > Jet Blast
Reload this Page >

Smoke Alarms

Jet Blast Topics that don't fit the other forums. Rules of Engagement apply.

Smoke Alarms

Old 9th Feb 2021, 09:44
  #1 (permalink)  
Thread Starter
 
Join Date: Jan 2003
Location: Southampton
Posts: 752
Smoke Alarms

I was woken up last night by the low battery alert in one of my smoke alarms.

Taking it down, I noticed on the back an expiry date. Now I knew that they had a life (this one was 7 years), but the date on this was December 2017.

One, I can't believe I have missed that date before, but two, how time flies. I didn't realise I'd had it that long.

So, just a reminder for everyone to check your alarms. You want them to work if needed!
Saintsman is offline  
Old 9th Feb 2021, 09:50
  #2 (permalink)  
 
Join Date: Sep 2015
Location: London
Posts: 345
I test mine regularly by allowing my daughter to cook dinner.
pasta is offline  
Old 9th Feb 2021, 10:00
  #3 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 3,496
I used to have a garlic detector in the kitchen. Had to stand on a ladder with a tupperware container covering the alarm whenever she cooked with garlic.
Ascend Charlie is offline  
Old 9th Feb 2021, 11:17
  #4 (permalink)  
 
Join Date: Mar 2008
Location: Richmond NSW
Posts: 1,301
It's not only the battery powered smoke detectors that have an expiry date. The mains wired ones as well.
Those may escape the scrutiny of the others.
gerry111 is offline  
Old 9th Feb 2021, 11:32
  #5 (permalink)  
 
Join Date: Sep 2009
Location: UK
Posts: 7,490
Is the expiry date on the battery or the smoke alarm? As CO alarms have a sealed battery and the device has a " use by date "

Ps my smoke alarm is tested EVERY Sunday morning, As I do like crispy bacon with my breakfast
Kiltrash is offline  
Old 9th Feb 2021, 11:43
  #6 (permalink)  
 
Join Date: Oct 2002
Location: West Wiltshire, UK
Age: 68
Posts: 412
Apparently the sensors degrade over time, so most have to be replaced after ten years, irrespective of whether battery powered or mains powered.
VP959 is offline  
Old 9th Feb 2021, 11:55
  #7 (permalink)  
Ecce Homo! Loquitur...
 
Join Date: Jul 2000
Location: Peripatetic
Posts: 12,075
https://www.safelincs.co.uk/why-shou...ter-ten-years/
ORAC is offline  
Old 9th Feb 2021, 12:25
  #8 (permalink)  
 
Join Date: Nov 1999
Location: UK
Posts: 1,697
No time at the moment to look this up, but as far as I know, smoke alarms use a mild radioactive source as part of the actual smoke sensor.

I don't know which element is used, but all radioactive elements have half lives, i.e. the time taken for the production of Alpha, Beta or Gamma particles by the source to reduce by half. Obviously as this happens the sensitivity of the sensor will reduce.
Uplinker is offline  
Old 9th Feb 2021, 12:48
  #9 (permalink)  
Ecce Homo! Loquitur...
 
Join Date: Jul 2000
Location: Peripatetic
Posts: 12,075
Uplinker,

Americium-241 with a half-life of just over 432 years. After 30 years under 5% will have decayed to neptunium.

It isn’t a factor in the usable life of a detector.
ORAC is offline  
Old 9th Feb 2021, 13:04
  #10 (permalink)  
 
Join Date: Oct 2002
Location: West Wiltshire, UK
Age: 68
Posts: 412
I strongly suspect that the main issue is dust. I have an aerosol can of smoke detector testing "smoke", and have found in the past that smoke detectors that fail when tested with this can usually be made to work OK if taken apart and cleaned. The snag is that newer smoke detectors are harder to take apart and clean, so the only real option when they get dusty inside is to throw them out and replace them.

FWIW, the aerosol testing "smoke" is, I think, a far better way of testing smoke detectors, as it tests the actual sensor itself, rather than just the electronic circuitry. A can lasts a long time if not being used professionally, the can I bought several years ago for around 10 is still about half full.
VP959 is offline  
Old 9th Feb 2021, 13:09
  #11 (permalink)  
 
Join Date: Jan 2010
Location: Edinburgh
Age: 83
Posts: 51
Murphy's law decrees that the smoke alarm wakes me in the small hours whenever I have an early start planned for climbing. Having replaced the battery and returned to bed, the beep continues. So I get up and replace the battery in the CO detector, return to bed, and the beep continues. So I get up, disable the intruder alarm, replace the relevant sensor battery, and return to bed. Except it's time to get up and go climbing after v little sleep. Manages that trick as regular as clockwork.
Murphy was an optimist!
DType is offline  
Old 9th Feb 2021, 16:40
  #12 (permalink)  
 
Join Date: Jun 2003
Location: LFBZ (for a while)
Posts: 731
Our CO detector went into suicide mode a while back. You can take the batteries out to shut it up, but it has some spring-loaded prongs that then make it impossible to put back onto its base. I've been told that a thick layer of conformal coating on the end of one of the batteries works well, though it's certainly not something I'd try myself. And before the safety nannies chime in, the great irony of this is that there is absolutely nothing in the house capable of generating CO, but California code requires the detector anyway. I assume that someone in the CA legislation has a brother in the CO detector business or something.
n5296s is offline  
Old 9th Feb 2021, 17:12
  #13 (permalink)  
 
Join Date: Apr 2006
Location: Lestah
Posts: 173
Originally Posted by Uplinker View Post
No time at the moment to look this up, but as far as I know, smoke alarms use a mild radioactive source as part of the actual smoke sensor.

I don't know which element is used, but all radioactive elements have half lives, i.e. the time taken for the production of Alpha, Beta or Gamma particles by the source to reduce by half. Obviously as this happens the sensitivity of the sensor will reduce.
Radioactive source was a component part of ionisation type smoke detectors. Such types were stopped from manufacture quite a number of years ago now. Prone to false alarms due sensitivity issues around a number of trigger scenarios as well as disposal issues. Costs to dispose Ions due to the active component contained within were large and that swayed the market strongly over to optical (line of sight) types.

As such, domestic smoke types are optical not ionisation as the norm. How long they last is down to the manufacturer recommendations.

A reputable manufacturer will explore internal component degradation over time based on measuring performance delta against know operating standard norm. The quoted 10 year date is generally accepted as a rule thumb without such recommendation.

CO fire detection nearer to 5-6 years again without recommendation. And any CO element measure in a combined smoke and CO detector is not to be assumed as an equal application measure of CO from say, a boiler. It is a useful measure in fire detection for decision making to prevent false alarms. The PPM of CO measured is hugely different between the two applications.

If you have a dB metre. You need 75dB minimum measured at your bed heads to wake you. If not, get more detectors with sounder on all floors of your home. Just one fitted downstairs in the kitchen with that door closed will not save you.
Local Variation is offline  
Old 9th Feb 2021, 17:19
  #14 (permalink)  
 
Join Date: Apr 2020
Location: Terra Firma
Posts: 7
Originally Posted by n5296s View Post
Our CO detector went into suicide mode a while back. You can take the batteries out to shut it up, but it has some spring-loaded prongs that then make it impossible to put back onto its base. I've been told that a thick layer of conformal coating on the end of one of the batteries works well, though it's certainly not something I'd try myself. And before the safety nannies chime in, the great irony of this is that there is absolutely nothing in the house capable of generating CO, but California code requires the detector anyway. I assume that someone in the CA legislation has a brother in the CO detector business or something.
You may be surprised what can create CO.
There was a very sad case a few years ago when an "electrician" had shorted out all the thermal fuses on an electric night storage heater.
Both the setting thermostat and overtemperture thermostat had previously failed closed, causing the heater's one-time thermal fuses to operate.
In bypassing the only remaining fail safe, the cast-iron core became hot enough to melt in places; part-oxidising carbon in the cast iron to produce CO.
One cold night the occupant of the apartment was killed by CO inhalation.

I can't post a link, but try visiting the heatinghelp[dot]com website. Chose the forum "The Wall" and search for "Carbon monoxide death, electric storage heater".
Even the precis there of the HSE report describes a real holes-in -the cheese event.


Rev
TheReverend is offline  
Old 9th Feb 2021, 21:39
  #15 (permalink)  
 
Join Date: Jun 2003
Location: LFBZ (for a while)
Posts: 731
You may be surprised what can create CO.
If the CO hadn't got him he'd have been hit by a meteorite while returning from collecting his lottery winnings. Talk about having your number on it...
n5296s is offline  
Old 9th Feb 2021, 21:51
  #16 (permalink)  
 
Join Date: Aug 2005
Location: Toronto
Posts: 176
Originally Posted by n5296s View Post
Our CO detector went into suicide mode a while back. You can take the batteries out to shut it up, but it has some spring-loaded prongs that then make it impossible to put back onto its base. I've been told that a thick layer of conformal coating on the end of one of the batteries works well, though it's certainly not something I'd try myself. And before the safety nannies chime in, the great irony of this is that there is absolutely nothing in the house capable of generating CO, but California code requires the detector anyway. I assume that someone in the CA legislation has a brother in the CO detector business or something.
As a director of my condo building, I was ordered by the Fire Marshall last year (oh wait, it was 2019 :-) ) to immediately go out and buy CO alarms for the apartments one floor immediately below the rooftop boiler room. She said that the city byelaw said two floors, but she was only enforcing the Ontario Fire code which said one! So it depends on whom you ask.

Under the aegis of the same lofty (volunteer) station in life, I can tell you from experience that smoke alarms are required by code (in Ontario at least) to be replaced every ten years. I usually go around with the fire safety contractors to make sure they are not changing them willy-nilly to add to the bill!

ve3id is offline  
Old 10th Feb 2021, 02:18
  #17 (permalink)  
 
Join Date: Aug 2005
Location: Toronto
Posts: 176
Originally Posted by TheReverend View Post
You may be surprised what can create CO.
There was a very sad case a few years ago when an "electrician" had shorted out all the thermal fuses on an electric night storage heater.
Both the setting thermostat and overtemperture thermostat had previously failed closed, causing the heater's one-time thermal fuses to operate.
In bypassing the only remaining fail safe, the cast-iron core became hot enough to melt in places; part-oxidising carbon in the cast iron to produce CO.
One cold night the occupant of the apartment was killed by CO inhalation.

I can't post a link, but try visiting the heatinghelp[dot]com website. Chose the forum "The Wall" and search for "Carbon monoxide death, electric storage heater".
Even the precis there of the HSE report describes a real holes-in -the cheese event.


Rev
There is a report on the court case here:
https://www2.theiet.org/forums/forum...&threadid=7152

Copied below:

"HSE is keen to make electricians and engineers aware of the possibility of electric storage heaters being the source of carbon monoxide (CO) poisoning. This follows the tragic death of a Scarborough tenant who died of carbon monoxide poisoning. An electrician who had carried out work on the heater a few days prior to the fatality was prosecuted for involuntary manslaughter. The judge ruled that there was no case to answer on the grounds that the mechanism by which the CO was generated could not have been foreseen by the electrician.

Speaking of the case, Michael Stephenson, Principal Specialist Inspector (Electrical) HSE Yorkshire and North East said: "In most domestic cases of carbon monoxide poisoning that HSE investigates, the CO is produced by an incorrectly installed or maintained gas appliance. In this case, there were no gas appliances and not even a gas supply to the flats. The police requested HSE's assistance to determine the source of the CO."

Subsequent investigation revealed that an electric storage heater with a cast-iron core was the source of the killer gas.

Mr Stephenson continued: "There was evidence that a ducted air electric storage heater had overheated and reached excessively high temperatures resulting in a very rare case of CO poisoning from an electric appliance. Electricians must be aware of the potential for this to occur."

Mr Stephenson stressed: "Anyone working on electric storage heaters with cast-iron cores should be aware of the mechanism by which CO may be generated in sufficient quantities to cause death. This tragic event should serve to remind everyone of the possible consequences of shorting out or by-passing safety devices."
ve3id is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.