More Smoke Alarm Advice

[Dave Liquorice]

The AICO mains, ionisation, wired interlinked, "non-replaceable" lithium battery backed up, smoke alarms are coming up to 10 years old so approaching "end of life". One has started beeping and has been removed (for the time being) and on investigation the nominal 3 V Li batteries are down nearer 2.6 V each.

Looking around it seems that for landings/hallways, where these smoke alarms are, the ionisation type is depreciated these days in favour of optical.

CPC have the batteries at just over £4 each inc VAT. Or I can get a new optical with user replaceable alkaline battery backup for around £27.

Presumably the ionisation type age as the amount of active Americium

241 declines but with half like of 432 years is that real problem? If I replaced the batteries would it be a problem at 20 years of age?

Presumably an optical sensor doesn't age?

Can't decide between replacing the Li batteries and thus keeping the Americium 241 out of land fill or dumping them (they work according to the "test" button) and consuming more resources in getting new optical.

[Brian Gaff]

Hmm, I have to say I've not found problems with the ionising type myself since many years ago, when an early one got very insensitive and made me wonder if the source had the capacity to damage the chip. It says on all my alarms, do not dispose of in general trash, take to a recycling centre. Brian

[ARW]

The reason they are swapped after 10 years is because of "dust build up" and to keep the manufactures in business.

BTW AICO tell you not to test their smokes with smoke cans as "they cause a film of grease on the detectors".

A new battery and the detector will be good for another 10 years.

[Andy Burns]

Drop the off at your local fire-station, they send them off for proper processing (they generally have a box of them chirping randomly in a corner somewhere).

[Roger Hayter]

I think it says that on all electronic equipment nowadays. WEEEE regulations or something.

[John Rumm]

Yup similar here - none are beeping, but getting close to the ten year mark.

The ageing is more about build up of dust and the life of other electronic components rather than the ionisation source directly.

Well chances are they would carry on working ok with a new battery.

However, how much time and effort is it worth to "repair" them compared to the new cost - especially if there is any doubt about their ongoing sensitivity (since you life may we depend on it)?

[Davidm]

Around here (Hertfordshire) the fire & rescue people will give people over 65 alarms for free, and even come and fit (sticky pad) them if you don't like climbing up a pair of steps (or balancing in a kitchen chair) - still for free..

[tabbypurr]

Ionisation detects a fire earlier, giving you more time to get out. The downside is they're oversensitive to normal kitchen events like well done toast. If yours isn't producing false alarms it's better than an optical detector. So if it works I'd give it a new battery.

Both types are affected by dust, but optical more so. It might appreciate a good blow.

Am decay is a nonissue. Keep it for centuries and it might be.

NT

[Dave Liquorice]

according

Went for 3 x Li rechargeables from CPC just over £12. Five minutes to install. Unit no longer bleeps and sounds when test button pressed. B-) I might waft some real smoke in its general direction one day.

Half life of Am is over 400 years but I suspect they are intrinsically "fail safe" as it's the current flow between plates due to the ionisation of the air that holds the alarm off. Take away the ionising radiation, current stops and the alarm goes off. The test button should break the circuit so should be a reliable indication all is well. Don't know how the test button on an optical one works.

Cumbria Fire and Rescue also do a home check and fit smoke alarms but they are the simple standalone battery only jobbies not mains interlinked ones.

[tabbypurr]

I didn't

I believe it's the other way round.

it doesn't test the detector

NT

[Dave Liquorice]

Nope, alpha radiation from the Am ionises the air, the plates have a voltage between them so the generated ions whizz off to their opposite charge plate causing a current to flow in the circuit between the plates. Smoke absorbs/slows some of the ions, reducing the current triggering the alarm.

So removing, or having much reduced radiation from, the Am would trigger the alarm.

So not a real test is it? B-)