What are the most reliable hardwired smoke alarms?

[NeverDie]

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So if you buy a new smoke detector every year, vs keeping the same one for 10 years, it will not necessarily give you better reliability. It might even be worse due to the chance of early life failures.
 
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In my opinion, you can't get away from the need for frequent testing of the smokes.  And you need to have enough smokes installed to give you adequate redundancy in the event that one does fail.  It's just the way it is.

 
 
I think I may understand what you mean about bathtub curves and the likelihood of any one smoke alarm failing in any given year.  I'll concede the point you're making.  However, if you try repeating your math with a set of 10 alarms, do you arrive at a different conclusion?  If you have no foreknowledge of a  reliability difference between between a $12 alarm and a $129 alarm (i.e. the expected failure rate for each is random and roughly 3% per year), then assuming the $12 alarms are replaced every year and the $129 alarms are kept for 10 years, I'm pretty sure the odds of four out of ten $12 alarms failing during the one year between replacements will be much lower than four out of ten $129 alarms failing over a 10 year period.  True?  Also, to upgrade the example, I suspect an alarm used over 10 years to have greater odds of drift and diminished sensitivity than one that's fresh every year.  I don't know whether the 3% figure would classify that as a failure, or whether it accounts for that all.  If the test button doesn't check for that, then your alarm might be impaired even if it tests OK.  In short, depending on what it actually tests and how well it tests,  even the recommended obsessive weekly testing using the test button might be delivering mostly false comfort.  I have a hunch UL217 might spell out what the test button should be testing, but I don't have a copy of UL217 that's recent, and the 1993 version I referenced is garbled in a lot of places.  
 
Also, I'll concede your point about the $129 alarm having two way wireless and the $12 doesn't.  That's a distraction though. I wasn't trying to argue that a $129 alarm that has features you value that a $12 alarm doesn't have should be priced at $12.  I doubt you would replace a $129 smoke alarm every year, and so I wanted to compare expected reliability from picking $129 smoke alarms and keeping them for 10 years (as most would do) versus the reliability of cheaper alarms that you might replace more regularly.  Also, my goal wasn't to beat up on the Elk alarm.  I merely used the Elk-6050  because its price helped keep the math simple (10x the price but over a 10x time period), and was looking for a real device so as to make a concrete example.  I don't think it will change the outcome regarding the comparative reliability of a set of 10 alarms if you prefer to pick some other ~$120 alarm that lacks two way wireless and other differences.  Anyhow, feel free to formulate a different concrete example using alarms with more comparable features.  As long as one is a lot more expensive than the other, the example (using a set of 10 alarms) could be adjusted by varying the replacement period, Unless my intuition is off,  the reliability math should still favor the cheaper alarms with the shorter replacement cycle.  Am I wrong?  The example becomes interesting if most people think it wouldn't make a difference, if in fact re-doing the math with a set of 10 smoke detectors turns out to show a big difference in system reliability.
 
By the way, I'm also not against expensive alarms per se.  I happen to think a more expensive smoke alarm might also be built with better components and/or with more manufacturing care, and so there's hope you might get more reliability.  Or maybe not, if UL217 sets the reliability target and consumers have no other information about quality and reliability.  This is where having actual public data would help steer people toward better, possibly more expensive alarms, or at least inform the tradeoff.  That's why I was asking, earlier in the thread, where I might find such data, if it exists at all.  At this point though, after searching (not exhaustively but pretty hard) and finding not even vague references to it, I'm doubting it exists.

 

[newalarm]

I think the main reason jurisdictions do not allow a low voltage system instead of line voltage smokes are the other factors. In an alarm system, if you don't maintain the system, pay for monitoring, replace the backup battery, or just shuts the system off because something is not working right, the whole system is down and life safety is out the window. This is especially the case with an Elk type system were it does a million things besides the alarm (home automation etc.) and it is so easy for system to have an issue that makes it a nuisance.
 
With a line voltage system, it is essentially a dumb system: it needs 120v and a backup battery in each unit and when one battery dies, that detector tells you.
 
For sprinklers, you really don't want them as your first line of defense. Once that goes off, you essentially have fire and or very hot temps and will end up with major water damage. You need the smoke detector to alert you of a situation to address it. Please note, this is very different than in Hollywood where sprinklers in an entire building can all go off at once if someone pulls a fire alarm
 
The flow detector on sprinkler main would be valuable to know if a sprinkler head went off by accident or defect, or if you sprung a leak.
 
Sprinklers scare the hell out of me. I just imagine them going off and spraying down all your stuff. Great if there is a fire, but a nightmare if it is an accident.

 

[Del91574]

Interesting discussion. I have come to have similar questions on the functioning of the ELK detector and raised these with ELK.
Here are the answers they provided.
 
- will the smoke detector work (detect smoke/heat and sound the built-in sounder) without the panel present? i.e. if there is no power for extended period, and panel shuts down due to exhausted battery.
[SIZE=11pt]The ELK-6050 will sound if there is smoke/heat present, but with no power to the panel, the alarm will not be recognized or reported.  The  Sound All™ feature also cannot be activated.[/SIZE]
 
- in such 'unsupervised' operation will the sound-all feature work or that is dependent on the panel?
[SIZE=11pt]The Sound All™  feature requires the M1 and wireless transceiver to be functional[/SIZE]

This is the exact reason why they would never be compliant for code purposes. They require the host system to be active in order to have the code mandated tandem ring work.
 
@ Work,
It's been a while, but I remember that many locales allow the requirement to be either (or both) a sprinkler system or required fire alarm detection, but most AHJ's require the latter as a means to evac the building unless there is a supervising FA to monitor the flow and/or generate an audible alarm to notify the occupants to evac.
 
My state mandates sprinklers in any residential building over 4 stories (habitable) or in a few municipalities, they require such if the home/development is too far from the local responding FD.

 

[Del91574]

I think the main reason jurisdictions do not allow a low voltage system instead of line voltage smokes are the other factors. In an alarm system, if you don't maintain the system, pay for monitoring, replace the backup battery, or just shuts the system off because something is not working right, the whole system is down and life safety is out the window. This is especially the case with an Elk type system were it does a million things besides the alarm (home automation etc.) and it is so easy for system to have an issue that makes it a nuisance.
 
With a line voltage system, it is essentially a dumb system: it needs 120v and a backup battery in each unit and when one battery dies, that detector tells you.
 
For sprinklers, you really don't want them as your first line of defense. Once that goes off, you essentially have fire and or very hot temps and will end up with major water damage. You need the smoke detector to alert you of a situation to address it. Please note, this is very different than in Hollywood where sprinklers in an entire building can all go off at once if someone pulls a fire alarm
 
The flow detector on sprinkler main would be valuable to know if a sprinkler head went off by accident or defect, or if you sprung a leak.
 
Sprinklers scare the hell out of me. I just imagine them going off and spraying down all your stuff. Great if there is a fire, but a nightmare if it is an accident.

The only difference between LV and HV detectors is the host system and how the code is interpreted by the AHJ.....nothing is prescriptive as far as stating you CAN'T use LV units to replace the HV units, the only caveat is they technically need to meet the same design criteria. The only time they are refused is if the AHJ states they want LV units for the reasons stated......but HV units can be removed and/or have major issues and never alarm, just like LV units.
 
Sprinklers are factually more effective in the event of a fire because they function while the fire is still in the incipient stage compared to when a detector really starts to function (not getting into the discussion of technology/pros/cons and how they vary here). Yes, there is possibility of water damage, however the overall results are far more benefitial compared to harmful...not to mention the design of the system risers have shutoffs and other items that are accessible to facilitate easy system shutoff by responders.
 
There's a reason why commercial fire alarm systems monitor flow and that 99.9% of the time generates a system evac that is not silencable.....if a flow goes off (barring a failure or leak which really doesn't happen in a manner detected by system flows-look at their design criteria, they only alarm when the flow is sufficient to equal the volume from a single tripped head) then there's an actual fire alarm event or someone snapped a head off.

 

[tmbrown97]

Yeah - in CA they've been a requirement in multi-dwelling buildings for years - all apartments; hotels and commercial buildings it's been as long as I can remember... it was about a year or two ago that they became required in ALL new construction.  My home was prior to that when it was deemed by my local city government that houses over 3K sq ft would need them - had to do with a set of railroad tracks between us and the fire department that could potentially delay their ability to reach us (though not sure why Sq. Ft. would matter in that situation).
 
I know that having a sprinkler go off isn't the best way to get people out of the building - that should be the earliest detection possible and can allow for such sensitivity as to allow false alarms even in the effort to save the most lives; however dispatch of emergency crews should have a little better error detection because IMO that should be secondary to saving lives - that's more about saving property.
 
And that's right - there's no way physically possible to set off every sprinkler in a building - not only would it be insufficient pressure to be useful, that's just not how they work.  They have a glass bulb or piece of metal that will pop when a specific sprinkler head gets hot enough - triggering only that sprinkler.  In most fires, only a single sprinkler is ever activated.  Also, that water is nasty stagnant water that's been sitting in the pipes for years.  Anyone with sprinklers should know how to cut off their supply in a hurry.

 

[Del91574]

Usually there is going to be some requirement to supervise the sprinkler, but that can also be done locally (no mandate to install a system in residential only for that purpose) unless the insurer requires otherwise.

Sprinkler water, while somewhat nasty in general, isn't that bad in a PVC based system, especially if it's flowed and tested regularly as required by code.

 

[ano]

For sprinklers, you really don't want them as your first line of defense. Once that goes off, you essentially have fire and or very hot temps and will end up with major water damage. You need the smoke detector to alert you of a situation to address it. Please note, this is very different than in Hollywood where sprinklers in an entire building can all go off at once if someone pulls a fire alarm
 
The flow detector on sprinkler main would be valuable to know if a sprinkler head went off by accident or defect, or if you sprung a leak.
 
Sprinklers scare the hell out of me. I just imagine them going off and spraying down all your stuff. Great if there is a fire, but a nightmare if it is an accident.

I live in a city that has required fire sprinklers in all new homes for more than 25 years.  I have never had a sprinkler go off accidentally nor have I ever heard or read that occurring.  When this occurs there is a flow sensor that triggers an outside bell, and I monitor it as well with my security system.  A sprinkler going off, like a smoke detector going off, will trigger a fire alarm.
 
A few years ago they conducted a study of fire deaths in my city for homes with and without fire sprinklers.  Using 15 years of data, they recorded 598 house fires.  Of these, 13 people died in homes without sprinklers, none did in homes with.
 
The average loss for a home with a sprinkler was $2,166 
The average loss for a home without a sprinkler was $45,019
 
The average fire sprinkler discharged 341 gallons of water before being shut off.
If firefighters had to put out a fire, they discharged an average of 2,935 gallons of water through hoses to put it out.
 
The cost to add sprinklers to a home being built in my city is about $0.80/Sq. Ft.

 

[Automate]

Interesting,  seems like dumping 341 gallons of water in a home would cause more than $2,166 damage even excluding any fire/smoke damage.

 

[NeverDie]

Even if the Elk wouldn't meet code for the reasons given by DEL, what about the Nest Protect? 

 

[NeverDie]

I seem not to be getting useable answers, so I'm moving on.  Thank you to those who contributed to the thread. 

 

[gatchel]

Enjoy. Sorry we couldn't help you.
 
I would just install more detectors if you are that concerned that existing failure rates and standards are not good enough. K.I.S.S.
 
If you come up with the "perfect scenario" please post back so we all can get an update

 

[Del91574]

Even if the Elk wouldn't meet code for the reasons given by DEL, what about the Nest Protect? 

The Nest, while UL listed, does not address what is contained in the adopted building codes which is going to dictate whether or not it would be an allowable substitution.
 
It may be true that there is no restricting covenant for hardwired/wireless interconnect, there is one for how the devices must perform, be supervised and also report trouble conditions.
 
There is no armor clad statement that can be made to say XX or YY is 100% usable in every municipality or application, because there's going to be multiple codes involved and many items that may or may not apply....is the area IRC or not? Which NFPA 72 is the area running? What does the fire marshal want? What does the building official want? What does the state allow in their general statutes?

 

[NeverDie]

Thanks, DEL.  I don't have the energy to run a gauntlet regarding a new technology that probably the AHJ's haven't even heard of, so I'll circle back in the future when it will be easier to sort out.

 

[Del91574]

Based on prior statements, I think you're putting the cart before the horse in this case. There's far more involved to this discussion and what can and can't be done and what is reliable and not reliable and comparting smoke detectors to smoke alarms.....

 

[NeverDie]

Based on prior statements, I think you're putting the cart before the horse in this case. There's far more involved to this discussion and what can and can't be done and what is reliable and not reliable and comparting smoke detectors to smoke alarms.....

 
I can appreciate how looking at the thread without knowing the background would create that sort of impression.  The reason for the jumbling of issues is that I was hoping to find a masterstroke that would achieve a number of different distinct objectives all at once.  Here's a briefer, more linear version:
 
Recently, I have (had) ten cheap ionizing hardwired smokes with battery backups, because the electricians said they were needed for meeting local code during a remodel in 2009.  I also have one smoke detector that's monitored by an alarm panel.  The idea of increasing my monitored coverage by adding a smoke detector everywhere I already have a smoke alarm (while keeping the smoke alarms as a separate system) seems unrealistically conservative (almost insane on the face of it), so I still have just the one smoke detector.  At least in 2009, the local code was (and may still be) similar to what it is in NJ.

In any case, I've had about one idiopathic false alarm per year with the cheap smoke alarms, and at minimum I wanted to avoid having any more.  In the course of researching causes for the false positives, I began to wonder about the potential (and causes) of false negatives as well (which is where this thread begins).  After looking into reviews on amazon, the smoke alarms I have (BRK 9120B's) clearly have a reputation for false alarms.  Digging further, the source of the false alarms seems most likely traceable to 1. power fluctuations and/or 2. dust accumulating in the smoke detection chamber.  I'm not sure what to do to mitigate possible power fluctuations (any suggestions?) on the incoming HV electric lines from the utility (per code, the smokes are on their own dedicated circuit), but I've stepped up my inspection and cleaning schedule.  As the false alarms weren't very frequent, it would take about a year or so to know if the more frequent inspections/cleanings were having any effect.  To improve my odds of completely dodging another idiopathic false alarm, I thought I would also upgrade the smoke detectors to ones which, if nothing else, would at least have less reputation for false alarms.  The FirstAlert 3120B (dual photodetecting and ionizing) smoke alarms are drop-in replacements (same wiring and connectors as the BRK 9120B's) and seem to get good reviews on Amazon, especially by people who previously had problems with false alarms.  I was about to do a simple swap-in with the 3120B's when I sensed this might be an opportunity to globally optimize with the monitored smoke detector system also.  However, somewhere in the course of this thread I got the impression it's still too soon for that chasm to be crossed.

The BRK 9120B's were placeholders until I could find better options.  I'm now swapping out the BRK 9120B's for $30 FirstAlert 3120B's and also $50 FirstAlert SC7010B's (photodetecting and carbon monoxide) alarms.   Late Saturday I swapped in one of each, and I'll swap in another one of each next weekend, and I'll continue swapping in a couple each subsequent weekend until done.   It's not a complete waste, because they will detect more threats better than the BRK 9120B's.  I am disappointed, though, that I couldn't do better.  I'll probably replace them all again in about 5 to 7 years as the SC7010B's approach end of life, and hopefully by then the options and prospects for a unified, monitored solution will be better than they presently are.  
 
In short:  It still seems odd to me that there are no "dual purpose" smoke alarms that can behave like smoke alarms for meeting residential code and simultaneously (without sacrificing safety) serve as supervised smoke detectors in a monitored alarm system.  Then I could have the benefits of both without the excessive duplication that presently seems required to satisfy code.  If designed properly, there's every reason to think such a unified system would be safer than what's commonly available, especially if it met or exceeded the same  UL minimum reliability and performance requirements of existing UL approved devices in both categories.