Smoke alarms: what's the latest?

[Another John]

Our smoke alarm started chirping in the middle of the night again -- just one very brief chirp, once every 50 seconds: I always take this to mean that it wants a new battery. It seems to need one at least once a year (which don't seem that good, since 'it never does anything'!)

I got this alarm several years ago now. Since the batteries it requires are those jolly expensive 9-volt zippo-lighter-shaped ones, I'm wondering idly about getting another.

Has the technology changed sufficiently for me to invest in a newer model (I see from a brief review that I won't get away with rechargeable AA batteries -- alarms seem to require heavy-duty jobs.)

John

[Count de Monet]

You are joking..........right?

[Mr Pounder]

Scrooge. The batteries are cheap.

{This reminds me to check my alarms}

Mr Pounder

>

[Toby]

Use a Lithium battery - from the comments seems to last about 5 years

per year or 7.4p per month, to help save you from burning to death in your sleep.......

If the alarm is old (10 yeears +), then it will prbably be best to replace it with a new one anyway.

You can get them with a bult in lithium battery that lasts for 10 years for about £15

That's £1.50 per year, or 12.5p per month, to help save you from burning to death in your sleep.......

[John]

> 88.8p per year or 7.4p per month, to help save you from burning to death

Get a good battery - I once bought a cheap one and it sounded the battery fail alarm straight away. They are a false economy and a waste of materials and shipping.

[Skipweasel]

Don't buy the really expensive 9V batteries, for a start - I've not found the last significantly longer. Aldi's alkaline sort are cheap and work for a couple of years at least.

However, if you're bothered, you can get mains units - though you should of course still have a battery backup. Some have very high capacity capacitor backup instead - which is in effect a rechargeable battery. They go on for ages and ages - at least weeks without power. You can interlink units throughout the house and choose a thermal alarm in "toast" areas.

for example. You may find the wiring bulky without the mounting base. They're usually powered from the lighting circuit so they don't go off when the sockets trip out.

[Bob Eager]

Duracell Procell alkalines are currently £11.29 for 20 from CPC. (code BT0389106). These last well over a year, so thats' about 57p a year.

Funnily enough, I just changed them in all of our alarms (we have six).

[pete]

> 88.8p per year or 7.4p per month, to help save you from burning to death in

Agreed, we've got the 10 year ones - if they do what it says on the tin I'll be very happy. Also they're handy for elderly people who can't reach, or don't feel confident balancing on a chair, to change the batteries in ordinary ones.

[Jules Richardson]

You can probably get mains one - I just picked up a CO detector[1] like that. It has a 9V battery as backup, too, but annoyingly doesn't take a rechargeable and charge it from the mains during 'normal' operation, which would be nice to have.

TBH, I'm not sure I'll replace the included battery when it eventually does go flat - the chances of there being a serious CO leak at the same time as the power goes out and my not noticing that the power's out seem rather remote.

[1] it has a built-in 7 year lifespan before it turns into a brick, which it didn't say on the outside of the box. Anyone know what the process is that renders the sensors unreliable and so makes the manufacturer want to do this? I assume it's not just a feature to sell more product, or they'd find themselves in trouble :-)

cheers

Jules

[John]

It could be something to do with the active element degrading over time. Isn't it radioactive?

[Mr Pounder]

No they don't. The alarm will chirp within 9 months.

[Skipweasel]

With a half-life of 432 years, other matters of concern may arise long before a lack of ionisation becomes important.

[Skipweasel]

OK - you must have odd alarms. Ours run for ages on them.

[Bob Eager]

No, CO detectors work on various principles, none of them involving radioactivity. Some use the photoelectric effect, some rely on oxidation (well, removal of oxygen), and some work using the lectrolytic effect. I think most of the ones we see are oxidation ones, and I guess the metal oxide degrades over time.

[Another John]

No, I wasn't really -- more, I was trying to say that if it's just sitting there "sniffing", rather than blasting off 85db, it's surely not using a lot of power? (I'm thinking clocks and their batteries, which

-do_ last for year IME)

The other thing that I didn't make properly clear was that (although I _do_ hate spending money), I wasn't so much interested in a cheaper alternative, as in finding out if the technology's changed ... and from the useful responses posted so far, it seems it hasn't: thanks a lot chaps! (I'll go get me high-quality 9v battery.)

John

[newshound]

I've just put in half a dozen of the ten year ones (more like a tenner I thought). Still good value if they do last.

[Matty F]

I use a cheap brand of 9v alkaline batteries (GBP 1.50 each). I write the date on them so I know they last about 3 years. I test the alarms with smoke about every 6 months.

[Mike Barnard]

Here's an interesting article on how these alarms work. 99% of household alarms will be ionising alarms.

may be quiet, but it IS doing something...

[Mike Barnard]

Lol, we test the alarm with cooking smoke fairly 'regularly'. Janet likes her food very well done.

[Bob Eager]

We have a mixture of ionising and photoelectric alarms, depending on location (this house has a peculiar layout, necessitating several alarms to ensure safe coverage).

And in the kitchen we have a heat rise alarm.