Ionization detectors use a small particle of nuclear waste to ionize the
smoke particles so that they will conduct a small current. When enough
particles are present in the detectors sensing chamber the detector goes
A photoelectric smoke detector can take two forms one works on
obscuration and the other works on back scatter or reflection. In the
obscuration type the smoke blocks or obscures the light source from the
photoelectric detection cell and the associated circuit drives the alarm
after detecting the loss of light on the photocell. In the back scatter
type the smoke reflects the light from the light source back onto a
photo cell that drives the detector into alarm.
In general the ionization type, which detects the smaller invisible
products of combustion, is quicker to respond to free flaming fuel
limited fires. The photoelectric type, which detects the larger visible
products of combustion, is faster to respond to smoldering or oxygen
Ionization detectors are much more prone to nuisance alarms caused by
cooking, painting, and similar activities.
I am about to get smokes for an apt. Electrician told me to just pick them
up. Found out that local code is within 20 feet of cooking apparatus or
steam from a bathroom that its photo type. I was wondering which one was
more sensitive for the rest of the apt so I went ionzation.
In hard wired models, battery only providing back up in case of AC
Alkalines are fine in smoke alarms, and my data shows with good makes
ie Duracell Ultra they'll last nearly 4 years; so well worth cost.
Manufacturers manual will list recommended types; lithium batteries
may also be usable provided their use sanctioned in user guide.
Wouldn't suggest otherwise as these alarms have extra component to
allow for mis fitting of lithium battery ie reversed polarity;
they have potential to explode so why this is so important.
Never use rechargeable loose batteries, as have wrong dischange
characteristics, and would not activate low battery beep as
required [for min 30 days in UK].
Low battery triggered when voltage hits 7.4V.
Difference in Ion & Optical been explained by other posters;
Ion now banned most of Europe, except UK & Eire.
Useful info on type selection/location at
On 13 Mar 2005 00:52:40 -0800, email@example.com (Gel) wrote:
Now that is a shame about ION. I know why, cause I remember how it
was a serious concern here in the US about 2 decades ago. I believe
the manufactures addressed the problem with documented proof about
Americaium after 10 operating life, and offering a recycling program,
but consumer's still might not be using them.
Just hear too many problems with Photos getting dirty and not working,
but then if you clean them too when you vaccum, that shouldn't be a
problem. But anyone here regularly vacuum their smoke detectors?
tom @ www.Love-Calculators.com
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