RANT: 10 year optical smoke alarms that aren't 10 years. - Page 1
Forum section: electronics / general

author: hamster_nz
author_rank: Super Contributor
timestamp: March 28, 2019, 10:30:44 pm
content: We built a house, and installed six 10-year optical smoke alarms.18 months later, three were on the shelf after beeping every 43 seconds at 2am, while I try to get replacements. Apparently the importer wouldn't help - I needed to go back to the electricians wholesaler with the electrican's invoice.So I tried the original manufacturer:QuoteYesterday I finally got the ducks aligned to allow replacement, and overnight another one started beeping at 4:00am, and then another at 5:30am (first cool night in a while).ARRGGHH!!!!

author: Halcyon
author_rank: Unknown
timestamp: March 28, 2019, 10:48:29 pm
content: Smoke alarms should last quite a while. I was talking to a bloke who works for a company installing, testing and certifying smoke and fire detection systems and he still sees ionisation type detectors which have in service since the 1980's and are still within spec.I had a similar issue to you when I moved into my new home. After about 4 or 5 months, two of the three smoke detectors I had installed started beeping in the early hours of the morning. This indeed was a low battery indicator (even though they are also hard-wired, they have 9 volt battery backup). Obviously they supplied the detectors with the cheapest, crappiest batteries they could find which had probably been sitting on a shelf for 5-10 years.After swapping them out with fresh batteries, I've never had a problem.The reason why it generally happens early in the morning is because it's usually the coldest part of the night and the drop in temperature also causes a slight drop in voltage, triggering the low battery signal. It's not a fault in the alarm itself, in fact, that is exactly what it's designed to do.

author: james_s
author_rank: Super Contributor
timestamp: March 28, 2019, 11:32:14 pm
content: The ones with the built in disposable battery are crap. I tried some regular 9V lithium batteries in mine that were supposed to last 10 years and they only went about half that. Now I use NiMH LSD "9V" batteries and charge them about once every 6 months as soon as the first one starts beeping.

author: Homer J Simpson
author_rank: Super Contributor
timestamp: March 28, 2019, 11:48:05 pm
content: Is that designed in ?Where they always start chirping at 2:00AM ?-K

author: Halcyon
author_rank: Unknown
timestamp: March 29, 2019, 12:28:07 am
content: Quote from: Homer J Simpson on March 28, 2019, 11:48:05 pmIt's not "by design" per se, the smoke alarms in most homes don't know what time/date it is. There is a threshold where a battery becomes "low" and triggers the low battery condition. Naturally over time, a battery will reach that threshold. Unfortunately at 0200hrs (the coldest part of the night in most homes where heating is not constantly running), the voltage will dip slightly. If the battery is already near that threshold, the dip in voltage might be enough to push it under and trip the low battery chirp.

author: floobydust
author_rank: Super Contributor
timestamp: March 29, 2019, 12:41:07 am
content: Take them apart, I find their optics get a fine dust on them.With old mains-powered ones the LED fades away, or the capacitive divider fails.Always check for product recalls, many smoke alarms get recalled if the don't detect. If they false alarm though, no one seems to care.

author: Halcyon
author_rank: Unknown
timestamp: March 29, 2019, 12:43:22 am
content: Quote from: floobydust on March 29, 2019, 12:41:07 amI make it a habit to change my smoke alarm batteries every 12 months. The batteries that come out of them are used in other devices until they are depleted.You can buy "smoke in a can" to test smoke alarms; it's probably not a bad idea to do this while changing the battery.

author: james_s
author_rank: Super Contributor
timestamp: March 29, 2019, 12:46:06 am
content: Personally I prefer the ionization type. There's one of those at our cabin that is at least 35 years old and still works perfectly, I set it off cooking sausage last time I was there.

author: Muttley Snickers
author_rank: Unknown
timestamp: March 29, 2019, 01:05:05 am
content: Quote from: james_s on March 29, 2019, 12:46:06 amSilly sausage.

author: hamster_nz
author_rank: Super Contributor
timestamp: March 29, 2019, 01:15:21 am
content: Quote from: james_s on March 29, 2019, 12:46:06 amCan confirm but am pretty sure that the replaceable battery ionization alarms are no longer allowed in rental properties by NZ law - they have to be 10 year ones. (quickly checks).Quote

author: james_s
author_rank: Super Contributor
timestamp: March 29, 2019, 02:19:37 am
content: Quote from: Muttley Snickers on March 29, 2019, 01:05:05 amArg, stupid autocorrect, fouls me up almost as often as it fixes things.

author: amyk
author_rank: Super Contributor
timestamp: March 29, 2019, 02:51:01 am
content: Quote from: Halcyon on March 28, 2019, 10:48:29 pmThe older ones used more radioisotope, but the newer ones have less, due to the cost and safety aspects.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 29, 2019, 03:12:42 am
content: It doesn't seem to matter what kind you buy. Either they will have a manufacturing or design defect and be subject to a recall, or within 5 years dust or insects will have messed up the sensor and causing false alarms all the time.I know because we have 30 smoke detectors in our condo building and I've seen it.

author: hamster_nz
author_rank: Super Contributor
timestamp: March 29, 2019, 03:43:58 am
content: Quote from: Alex Eisenhut on March 29, 2019, 03:12:42 amFunny you should mention insects... on of my alarms had 'grown' it's own dust filter... I though that was the cause of the first failure.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: March 29, 2019, 04:06:51 am
content: Here in Australia, we get a reminder to change the batteries in our smoke alarms at the change of prime ministers

author: floobydust
author_rank: Super Contributor
timestamp: March 29, 2019, 04:20:24 am
content: Quote from: Alex Eisenhut on March 29, 2019, 03:12:42 amI have some "American Sensors" ionization models that make their own smoke and false triggerThey are a cheap chinese build and the mains-resistor runs super hot 24/7, parts bodged on the pcb bottom etc. It also melted the connector. Bitched about it to safety and regulatory- but there is no requirement for component operating temperature, or a fuse, or build quality.Companies import them and proceed to get crap safety approvals for great profit. It was all swept under the rug, no recall issued.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 29, 2019, 05:33:34 am
content: Quote from: amyk on March 29, 2019, 02:51:01 amThat isn't a factor in the lifetime. Americium-241 has a half-life of 432 years, the decay in 20 or even 40 years is not enough to impact functionality. The "10 year" lifetime is mostly based on an "estimated" design lifetime of the electronics and potential fouling of the detector chamber. A 40 year old device that still operates is just as good (or 93% as good) as a new one, but the same will be true of today's detectors in 40 years. How many of today's detectors will still have functioning electronics in 40 years is another issue, and of course the ones with sealed lithium batteries won't work.

author: Electro Detective
author_rank: Super Contributor
timestamp: March 29, 2019, 08:27:56 am
content: After you deal with temperamental/crap batteries, dust, and insect invasion, smoke alarms should behave themselves, and not chirp at 3 amor... ignore the above and just buy and fit new ones every 12 months > no thinking required, and shouldn't break the credit cardFWIW: I've seen mains powered units with battery backup go 15 to 20 years (and still going btw) if serviced,they pass every test and simulation, including real deal kitchen stove fires many meters away

author: duak
author_rank: Super Contributor
timestamp: March 29, 2019, 06:19:28 pm
content: After a renovation, we had three spiffy new smoke detectors installed. Just after install there was an earthquake at 1 AM. About 3 hours later, the smoke alarm went off for no reason. It happened again once more and then settled down. After three years or so, one has crapped the bed. It would intermittently throw a replace battery warning but then started throwing false alarms, usually at night. Go figure.

author: Red Squirrel
author_rank: Super Contributor
timestamp: March 29, 2019, 06:24:13 pm
content: Just occurred to me that I put a bunch of 10 year ones in my house when I moved in thinking "wow by the time these die I'll be in my 30's!" and here I am close to 10 years later at 32. I feel old now. 10 years seemed like such a long time but went by so fast.They'll probably start chirping on me sooner or later.

author: apis
author_rank: Super Contributor
timestamp: March 29, 2019, 09:02:42 pm
content: They replaced our old smoke alarms with optical ones. Within a few months it went off for no reson when I weren't home. A neighbour called the fire department. Luckily they were used to this so they called me first and asked me to go home and check before they sent out people. Would have sucked to come home to a kicked in door.Installed a new ionising smoke alarm again, have worked flawlessly just like the old one (and all other ionising alarms I know of).

author: Electro Detective
author_rank: Super Contributor
timestamp: March 29, 2019, 10:37:09 pm
content: I keep a couple of decent quality pre-tested battery powered spares on hand, just in case any mains units decide to give grief at the wrong diagnostics timeThe plan is to use double sided thick foam style tape to attach it temporarily to the top of the disconnected suspect unit, till the next day or asapThis way the temp unit is in the correct position, and no mounting headaches or possible damage to the ceiling, to make more work...FWIW: I keep the spares where the WC/toilet/dunny paper is stored alongside the fire extinguisher,otherwise like most 'spares' they'll never be found when you need them

author: james_s
author_rank: Super Contributor
timestamp: March 29, 2019, 10:48:15 pm
content: Quote from: Red Squirrel on March 29, 2019, 06:24:13 pmThe next 10 years will go by much faster than the last.

author: hendorog
author_rank: Super Contributor
timestamp: June 09, 2019, 09:12:49 am
content: Quote from: hamster_nz on March 28, 2019, 10:30:44 pmSo I was down at my mothers place this weekend. She was complaining about a random beep which I tracked down to a weird modern looking smoke alarm in the garage. At the time I'm putting two and two together as I remembered this thread.She told me it was supposed to last 5 years and she got it from Mitre 10 a couple of years ago. No docket/receipt etc, and no writing of any type on the alarm either. I opened it up and the battery tabs were spot welded.I rocked on down to Mitre 10 in Timaru, walked up to the service counter and said "My Mother got this smoke alarm a couple of years ago..."Didn't finish the sentence, she had turned around and started fossicking in a cupboard. So I stopped talking and just stood there feeling like a right pillock. WTF is going on...Then she pulled out a box, opened it up and handed me a new smoke alarm.Happy days

author: soldar
author_rank: Super Contributor
timestamp: June 09, 2019, 11:40:49 am
content: Quote from: blueskull on June 09, 2019, 09:15:04 amThe question is if a MOSFET blows up does it trigger the fire alarm.In this or any other thread.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 09, 2019, 06:17:53 pm
content: Quote from: james_s on March 29, 2019, 10:48:15 pmUnfortunately true, wish there was a way to slow it down. Does dragon glass work on grim reapers?So far so good with my detectors but I probably should be considering changing them. I'd actually like to do a wired system and wire them all to a central panel where I can have it set an alarm in my monitoring system to tell me which one went off. Could have it send an email on my phone too so I get an alert.

author: tooki
author_rank: Super Contributor
timestamp: June 10, 2019, 11:38:27 am
content: Quote from: james_s on March 29, 2019, 12:46:06 am...which is precisely the advantage optical type smoke detectors have: fewer false alarms.More expensive smoke detectors use ionizing and optical detectors (and sometimes heat detectors as well) to be less prone to false alarms, e.g. for in/near kitchens. I remember how in my last apartment in USA, I had unscrewed the smoke i.e. detector from the ceiling (so it was dangling from its mains wires) to that when I wanted to sear a steak on cast iron, I could seal a ziplock bag over it...

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 10, 2019, 11:54:07 am
content: Quote from: james_s on March 28, 2019, 11:32:14 pm5 years is a significant improvement in my book. Changing batteries every 6 months would drive me crazy and luckily has never been needed. I need to change them every few years and use bog standard cells. It's probably about 3-5 years.

author: apis
author_rank: Super Contributor
timestamp: June 10, 2019, 12:32:06 pm
content: Quote from: tooki on June 10, 2019, 11:38:27 amA smoke alarm that goes off because of smoke from cooking isn't a false alarm, it's detecting exactly what it's intended to detect: smoke.

author: madires
author_rank: Super Contributor
timestamp: June 10, 2019, 03:06:39 pm
content: We have also fun with smoke alarms (required by regulations). IME 9V alkalines last about 1.5 to 2 years. Can't say anything about 9V lithiums yet, started using them 2 or 3 years ago. Some smoke detectors have gone bonkers after a few weeks or months. It wasn't an empty battery, neither a degraded detection chamber (another feature of the smoke alarm's IC). It seems that a few are simply duds. Most are running fine for years.

author: tooki
author_rank: Super Contributor
timestamp: June 10, 2019, 09:22:43 pm
content: Quote from: apis on June 10, 2019, 12:32:06 pmExcept... wrong. There are multiple kinds of smoke. An ideal fire safety sensor can distinguish between the smoke from a house fire, from a major cooking fire, and smoke from cooking at high temperature. Optical and combined smoke detectors already do quite a good job of this, but in kitchens, modern best practices are to use heat detectors in addition to or instead of smoke detectors.Ionization smoke detectors are incapable of distinguishing different types of smoke, and react substantially to many aerosol-like cooking fumes that aren't actually smoke (in addition to actual smoke). Optical smoke detectors are relatively insensitive to the low-density aerosols and cooking smoke, whereas actual fire smoke tends to be quite dense, and thus easily detected by an optical detector.Anyhow, if a smoke detector goes off when in fact there is no fire, then itisa false alarm and thus a "nuisance alarm", which should be avoided at all cost. (You do not want people disabling smoke detectors because of excessive nuisance alarms!!!!)

author: nfmax
author_rank: Super Contributor
timestamp: June 10, 2019, 09:32:53 pm
content: I was looking at a rack of assorted '10 year' smoke detectors for sale in B&Q one day, when I heard the unmistakable sound of the once-every-two-minutes 'battery low' beep. Coming from one of the 50 or so in front me, but which one? Don't want to buy that one! Don't really want to buy one of the same model either. I left it for another day.

author: james_s
author_rank: Super Contributor
timestamp: June 10, 2019, 10:54:07 pm
content: Quote from: tooki on June 10, 2019, 11:38:27 amI burned the sausage and it made actual smoke, had I not been standing right there the alarm would have been a welcome warning that something was about to catch fire. I've only ever set it off that one time despite it being just a few feet from the stove, I don't consider this to be a false alarm.

author: Circlotron
author_rank: Super Contributor
timestamp: June 11, 2019, 12:54:19 am
content: Quote from: Muttley Snickers on March 29, 2019, 01:05:05 amHe said *cooking* a sausage, not =looking= like one.

author: apis
author_rank: Super Contributor
timestamp: June 11, 2019, 02:14:18 am
content: Quote from: tooki on June 10, 2019, 09:22:43 pmI think your cooking skills might be better than mine.I suppose it makes more sense to think of them as fire alarms rather than smoke alarms but I haven't really experienced the alarm going off except when burning things and the air being noticeably hazy. I've noticed my air filter unit, which has a particle sensor built in, reacts to cooking though. I'm not sure what sort of sensor they use.

author: tooki
author_rank: Super Contributor
timestamp: June 11, 2019, 08:27:18 am
content: Well, the best sensors for fire detection in kitchens are heat sensors, which look for a rapid and significant rise in air temperature. (Cooking, even with copious smoke, won't produce the extent and speed of temperature rise that an actual fire does.)As for my cooking skills: I'll proudly admit that I'm a very good cook. Part of that is not being afraid of high temperatures, which do sometimes produce visible and palpable smoke (like when searing meat on cast iron).

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 17, 2019, 11:05:33 am
content: Are there any affordable Smoke dedectors who use a Bus System for Power and Data?We have a 4 Floor Building and I want see where the Alarm goes off.