Smoke detector battery replacement

[JSUPreston]

When the new laundry room was put on my house (believe it was '05), we had to have new hardwired detectors installed. Part of local code. They were installed with some el-cheapo brand battery that apprently came in the package.

Well, I've been meaning to change them but kept forgetting, until both units started chirping about a month ago. So, I went 4 to 5 with a HF grade battery in mine as a backup. Put in a set of Energizers this time around and will probably wait for the chirping to begine before replacing those.

Thing that irritates me is that due to a strange floor layout, the bedroom detector for the kids' rooms is less than 20' from the kitchen. Just getting the kitchen a little warm from cooking can set the blasted things off.

[Rich P]

Loring,

Not sure where you buy your batteries, but I just picked up an 8 pack of Alkaline Duracells with a "best before" 2014 date at Costco in Mountain View CA for $13.99 plus tax. That's about $1.75 each. Since most of the ones I installed last year were still putting out 9 volts, I figure I'll get two years of usage minimum before they start to trail off. At that rate it would take a while to get a payback on the higher cost/longer life units (other than convenience).

As regards design life, looks like the NFPA "strongly recommends" replacing units after 10 years because of "aging of the electrical components". Seems to me if the test button is pressed and the alarm sounds things should be ok. Or does the silicon really get "old and tired" after 10 years?

The 10 year "rule" sounds very much like a CYA move, just like the manufacturer's recommendation on the springs on my garage door hinges. Plus it helps keep the folks who make this things in the game.

Rich

[MilDoc]

When we moved here the alarms were wired without battery backup. I removed all and replaced with battery units. Wired "only" seems rather dumb to me.

I check function every 3 months with a "mini" smoke candle, but replace batteries only when one chirps.

I replace all every 7 years rather than 10. They DO lose their function, and a electronic geek friend of mine explained that the test button ONLY tests the circuitry, NOT the smoke detecting ability. Thus the 10 year replace recommendation. I like my house, so 7-8 years seems to let me sleep better.

[LCHIEN]

Loring,

Not sure where you buy your batteries, but I just picked up an 8 pack of Alkaline Duracells with a "best before" 2014 date at Costco in Mountain View CA for $13.99 plus tax. That's about $1.75 each. Since most of the ones I installed last year were still putting out 9 volts, I figure I'll get two years of usage minimum before they start to trail off. At that rate it would take a while to get a payback on the higher cost/longer life units (other than convenience).

As regards design life, looks like the NFPA "strongly recommends" replacing units after 10 years because of "aging of the electrical components". Seems to me if the test button is pressed and the alarm sounds things should be ok. Or does the silicon really get "old and tired" after 10 years?

The 10 year "rule" sounds very much like a CYA move, just like the manufacturer's recommendation on the springs on my garage door hinges. Plus it helps keep the folks who make this things in the game.

Rich

i probably overstated the price - i think in double or quad packs they cost around 3 bucks at the local box store, the eight and 12 packs seem to be significantly cheaper.

On your other issue, the test button probably really just tests the circuits, but not the sensor. So if it beeps what its telling you is that the the button works, the battery is good and some of the circuitry is OK.

The sensor is the hardest thing to test in products - Its very difficult in the million dollar sensor systems we make at work as well as in $20 consumer products. Basically you want to test it by simulating the thing that makes it go off. Good sensors only sense the thing they are meant to sense and ignore everything else. So its hard to make it think its working by using electronics to stimulate it. Blowing smoke into it is the best test, but not very practical...

The sensors used in most smoke detectors are some mildly radioative ioniziation sources. I guess they do degrade over time. They just don't suddenly quit but they get less sensitive. So how much sensitivity are you willing to lose before you declare it bad??? Radioactive items have half-lives, a recognition that they go down exponential decay- where the rate of decline decreases over time. Its also the way batteries go down and probably drug potentcies etc. so to me expiration dates are just ridiculous, they should give half-lives of batteries and drugs. But the average stupid joe just wants a pass fail answer.

So i think the advice to replace after ten years is probably good.

[Rich P]

As Paul said, the only real way to test is "smoke em'". I have a detector in my workshop/garage which is 20 years old. On (relatively) cold days here in Northern Cal, I heat the space with a kerosene heater which tends to smoke a bit on startup. I have to stand by and fan away the startup soot or else the detector goes off. Perhaps a sooty candle is the best test? Or we could fork over a few bucks for new ones and hope that the latest batch from China is better than the last one from Taiwan. It's an interesting part of modern life when a simple question about batteries turns out to be an exploration of the basis of the technology that uses them!

Maybe someone should start a poll..."Who grew up in a house without smoke detectors and lived to tell about it?"

Yeah, I know they have saved lives but why does it have to be so hard?

[MilDoc]

Maybe someone should start a poll..."Who grew up in a house without smoke detectors and lived to tell about it?"

Yeah, I know they have saved lives but why does it have to be so hard?

Well, when I was around 2 years, the apartment building we lived in caught fire. All escaped. But it was 2 story, easy to get out of with multiple exits.

No fires since then. But as soon as detectors came out I installed (dual mode) ones in my mom's house, and everywhere I've lived. Plus CO2 detectors.

[billwmeyer]

As Paul said, the only real way to test is "smoke em'". I have a detector in my workshop/garage which is 20 years old. On (relatively) cold days here in Northern Cal, I heat the space with a kerosene heater which tends to smoke a bit on startup. I have to stand by and fan away the startup soot or else the detector goes off. Perhaps a sooty candle is the best test? Or we could fork over a few bucks for new ones and hope that the latest batch from China is better than the last one from Taiwan. It's an interesting part of modern life when a simple question about batteries turns out to be an exploration of the basis of the technology that uses them!

Maybe someone should start a poll..."Who grew up in a house without smoke detectors and lived to tell about it?"

Yeah, I know they have saved lives but why does it have to be so hard?

I grew up in a house with no smoke detectors, but my grandsons almost didn't. My daughter had no smoke detectors and it almost cost her and her 2 sons their lives. She woke up before 6 in the morning and groggily knew something was wrong. She got up and got her and her 2 sons out of the house with the back end of the house fully ablaze. All three had traces of smoke in their airways. The EMT's and the firemen all said it was a miracle they had gotten out of the house and that a few minutes more and they wouldn't have. It seems as though smoke inhalation puts you asleep further. My daughter is not an early riser and neither were her kids, especially on a weekend where they stayed up late watching movies. My view is that her Guardian Angel woke her up.

I will never gripe about the price of smoke alarms or battery replacement. They are mandatory by my code. Don't take chances, it isn't worth it.

Bill