Smoke Alarms

[imroberts]

I've been living in my property for about 2 years now and installed a couple of Kidde smoke alarms (this model - http://www.kiddesafetyeurope.co.uk/utcfs/ws-401/Assets/Smoke Alarms/0915UK.pdf) when I moved in, one in the lounge and one in my hallway between my bedrooms and the bathroom.

Over the past month or so, the one outside the bathroom has started going off near enough every time I get out of the shower and open the bathroom door. I am aware that steam particles can set off smoke alarms however find it odd that this has only started recently

I'm looking for new alarms however I'm confused what to buy. My current alarms are standard ionisation alarms. I've noticed a lot of the dearer ones tend to have photoelectrical or optical sensors, however from reading up these seem to be *more* succeptible to steam rather than less, therefore I'd be best off sticking with ionisation type alarms?

What would people recommend?

 

[Spark123]

Ionising are designed to alarm with more dense smoke than ionising.
I imagine ionising will become more sensitive over time owing to the half life of the radioactive source inside them decaying down giving less disintigrations per second for the detector to count.
I can't imagine getting steam into it will do it any favours tho, I take it you have an extractor fan? Could do with replacing the smoke anyway.

 

[ColJack]

given that the americium has a half life of 432 years, I don't think it's running out of alpha particles just yet..

 

[Spark123]

Depends on the size of the source you begin with too
I suppose the detector is more likely to fail first tho, and you have to remember that these things end up in landfill.

 

[ColJack]

makes no odds..
it still takes 432 years to fall to half of the starting particle output..
while I don't have the specs of the smoke alarm available, I recon that they'd build in a tollerance of a few % just to be sure.. so at 2%.. that's still 8.64 years...

 

[Spark123]

Not quite that simple as the half life follows an exponential scale so the DPS will fall off quicker at the start.
Detector efficiency does make odds, if it requires so many counts per second (or minute) to stay alive and the logic doesn't recieve that then it will trip it, remembering at best a single position detector will only count approximately 20% of the emmisions.