CO alarms.

[John B]

[G. Morgan]

Subject: Re: CO alarms. Newsgroup: alt.home.repair => John B I keep my CO tester out-of-use most of the time. It's in a workshop drawer,

Are you talking about a test instrument or a detector (life-safety device)?

[newsgroups01REMOVEME]

For like 10 bucks, is it worth it? I mean if the smoke detector meant to be replaced after 10 years(why now some come with 10 year batteries so you just toss when the battery dies), you might be gambling with lives.

Just say 10 bucks is cheap.

later,

tom @

[newsgroups01REMOVEME]

Good point, I didn't go looking for the nfpa stance, but if you are right, this could be ground for insurance companies failing to pay benifits.

:(

later,

tom @

[John B]

[George E. Cawthon]

Who says it is meant to be replaced after 10 years? Not on the unit. Not in the instruction manual. It is an ac wired unit intended for long term use. Give it a test like the instruction say and if it passes it is ok. Blindly following some arbitrary rule for replacing the unit is not only stupid but wasteful of resources. Test the damn thing.

[Gel]

I have NFPA document [can't see on website]detailing sound logic for the 10 year cycle. Its down to the MTBF rating. In UK all smoke alarms have to have their replacement date marked on product label, which is 11 years from manufacture ie 1 year allowed for shipping/storage etc.

Alarms like most electronics are getting more features for lower prices year on year, so replacement makes sense.

Bear in mind too majority of householders never carry out any alarm maintenance as detailed in manuls. Causes alarms to become over sensitive ie go off for no apparent reason, which p***s off householder, who may well then disconnect from AC power/remove battery.

On CO ALarms most CO cells have max life of 6 to 7 years and many will shut down via in built firmware.

AGa> > > >

[Pop]

===> MTBF is NOT ten years. MTBF alone does NOT predict end of life for equipment. It DOES predict the earliest time, on the left of a bell curve, when a component IN the equiment might fail. ...

===> I would like to see your source on that, or at least some reference to a source. I dispute the numbers.

... What research? What brands of CO alarms are you finding that do NOT employ the UL/CSA/EC/ any safety rating? If you bought such a device in the UK or in North America, you bought an illegal device which cannot be sold to you legally. I would like to know where you found this information.

Pop

[Ken]

Text contained in the link:

Why NFPA recommends home smoke detectors be replaced after 10 years:

Smoke detectors are one of the most important safety features of your home. Properly installed, working smoke detectors will give you the early warning you need to safely escape from a fire. But how do you make sure your detectors are working? One important way is to replace them after 10 years.

As electronic devices, detectors are subject to random failures. Product, installation, and maintenance standards are used to assure products work as designed despite this. Part of the technical basis for the first detector product standard was an assessment of expected failure rate, estimated at four per million hours of operation or one every 30 years. Early field studies of detector reliability, notably by Canada's Ontario Housing Corporation, confirmed the essential accuracy of this estimate, restated as a 3% failure rate per year. This means a very small fraction of home smoke detectors will fail almost immediately, and 3% will fail by the end of the first year. After 30 years, nearly all the detectors will have failed, most years earlier.

How soon should you replace your detector? This is a value judgment. Only 3% of detectors are likely to fail in the first year, and annual replacement would be very expensive, so that doesn't make sense. At 15 years, the chances are better than 50/50 that your detector has failed, and that seems too big a risk to take. Manufacturers' warranties for the early detectors typically ran out in 3-5 years. So, in ten years there is roughly a 30% probability of failure before replacement. This seemed to balance safety and cost in a way that made sense to the responsible technical committees.

If a 30% failure probability still seems too high, remember that replacement on a schedule is only a backup for replacement based on testing. A national study found home smoke detectors, when they fail, tend to fail totally, as opposed to hard-to-detect creeping failure, such as a loss of sensitivity.1 Regular monthly testing will help discover detector failure as well as a dead or missing battery. You can replace your detector when it needs replacing.

The same study showed all the inoperable detectors tested in 1992 were at least 5 years old and predated a 1987 change in product standards that reduced sensitivity to reduce nuisance alarms. Changes in detector chip design, among other improvements, make it likely that electronic failure now occurs at a rate much less than 4 times per million hours of operation.

Replacing detectors after 10 years protects against the accumulated chance of failure, but monthly testing is still your first, best means of making sure detectors work. Today's detectors are even less vulnerable than the original detectors. Regular maintenance of the more sophisticated systems used in larger buildings can keep them working very reliably for many decades.

1 Julie I. Shapiro, Smoke Detector Operability Survey, Washington: U.S. Consumer Product Safety Commission, October 1994 revised.

[Main Man]

UL & Kitemarked {A British Quality Standard] CO ALARMS are sold in UK, all have to be "CE" marked;{European Compliance with ceratin European Elec Safety Standards known as CEN's}

UK Government arm have done extensive Research on CO Alarms long term reliability, and until this Govt Dept known as the HSE, are happy it won't get added to our Building Codes alongside Smoke & Heat Alarms.

Some well known brands, also available in US, go out of spec after 1 year; they are measuring to the current British Standard BS7860.

SEE

2 brands passed muster; Nighthawk{Kidde} and SF; latter only sold in Europe I believe.

Tests were done by Research arm of main UK Gas Utility, Advantica, under contract to HSE.

[Pop]

Ken wrote: ...

Going on 11 years old, but that should be "good enough" data to be current, right? Nothing ever changes.

[tom]

NFPA Does:

[George E. Cawthon]

Yes, but the site also says that over half of the fires with deaths had no smoke alarms and that the failure of the alarm to sound was most often the result of a dead, disconnected, or missing battery. So you are already down to less than 25 percent likelihood of failure if you have a smoke alarm and it has a good battery.

The replacement every 10 years is based on a rather faulty understanding of electronic failure rate. The failure rate is nothing like a continuous rate, but they base there recommendation of 10 year replacement on a continuous failure rate.

They indicated that an early test showed 1 failure per 30 years of operation (no problem there). They interpreted this as a 3% per year failure rate with 30 % failure rate by 10 year. This isn't likely because a steady failure rate is not typical of electronic equipment. Everyone know that electronic stuff suffers a high initial failure rate and a low failure rate for a long or very long period and a high failure rate near the end of the lifetime. That's why you can buy a 30 year old radio or hi-fi and expect it to work. if it doesn't fail in the initial year. If a smoke alarm doesn't fail in the first month or two and certainly the first 1-3 years, it will last long past 10 years. Since the estimate is 1 failure per 30 years, most failure (after initial failures) would likely occur sometime after year

20 or year 25. And of course some would be still operating at past year 35.

[tom]

For a family/home owner to take the initiative to install smoke alarms, test and clean; isn't a 30-50% predicted failure rate high enough motivate that same home owner to replace them?

I have multible smoke alarms in my house, the problem I've seen is when a smoke alarm is working 100%, by the time they sound(based on serverity of fire and distance between the smoke source and alarm, etc, etc), the house is getting filled with smoke. I've seen tests where by the time the occupents started down the stairs, there were no stairs visible.

Now factor in I have areas in my house where number of smoke dectectors is 1. If that fails, the delay time is now greater, proving for a more differcult egress. I have a small house, and yet I have 7 smoke detectors, if the first floor fails and the hall, 2/7 still less than 30% possible failure rate prediction for a

[George E. Cawthon]

Gees, 7 detectors in a small house? must really be paranoid. What to you do or have in your house that you fear fire so much? You miss the whole point, the 10 year replacement idea is a fraud. You seem to have missed all the important points of the NFPA. First, you aren't likely to have a fire and second, if you have a smoke detector and it is hooked to an operating battery, you are not likely to have a fire death. Time to quit this argument. You should transfer your worries to more common causes of death and injury.

[clifto]

From my Nighthawk manual, page 1-6:

"While it is not required, on occasion you may wish to observe and become familiar with your alarm's response in the actual presence of carbon monoxide or Gas. The best and safest way to do this is with either a cigarette or an incense stick."

[tom]

4 bedrooms, one in each upstairs hallway, one there. downstairs in living room, one there basement, one there.

I pulled out the 10 year old ac powered ones when I moved in and upgrade them all to ac/battery backups. I plan soon to have a heat detector fire alarm installed in my attached garage. That would move it up to 8.

No worries, just precautions. Smoke detectors are cheap, and every room should ahve one(minus the nuisence ones, then they should be heat detectors).

later,

tom