All smoke detectors consist of two basic parts: a sensor to sense the smoke
and a very loud electronic horn to wake people up. Smoke detectors can
run off of a 9-volt battery or 120-volt house current.
Ionization smoke detectors use an ionization chamber and a source of ionizing
radiation to detect smoke. This type of smoke detector is more common
because it is inexpensive and better at detecting the smaller amounts
of smoke produced by flaming fires. Inside any ionization detector is
a small amount (perhaps 1/5000th of a gram) of americium-241. The radioactive
element americium has a half-life of 432 years, and is a good source of
An ionization chamber is very simple. It consists of two plates with a
voltage across them, along with a radioactive source of ionizing radiation,
like this: The alpha particles generated by the americium have the following
property: They ionize the oxygen and nitrogen atoms of the air in the
chamber. To "ionize" means to "knock an electron off of."
When you knock an electron off of an atom, you end up with a free electron
(with a negative charge) and an atom missing one electron (with a positive
charge). The negative electron is attracted to the plate with a positive
voltage, and the positive atom is attracted to the plate with a negative
voltage (opposites attract, just like with magnets). The electronics in
the smoke detector sense the small amount of electrical current that these
electrons and ions moving toward the plates represent.
When smoke enters the ionization chamber, it disrupts this current -- the
smoke particles attach to the ions and neutralize them. The smoke detector
senses the drop in current between the plates and sets off the horn.
Speaking of alarms, whenever the words "nuclear radiation" are
used, an alarm goes off in many people's minds. The amount of radiation
in a smoke detector is extremely small. It is also predominantly alpha
radiation. Alpha radiation cannot penetrate a sheet of paper, and it is
blocked by several centimeters of air. The americium in the smoke detector
could only pose a danger if you were to inhale it. Therefore, you do not
want to be playing with the americium in a smoke detector, poking at it,
or disturbing it in any way, because you don't want it to become airborne.
Established in 1975, ABCO Fire supplies
fire protection and prevention needs for nearly 50,000 customers in the manufacturing, retail, government,
and marine industries. They provide portable and fixed systems and compliment
these products with inspection, maintenance, and certification services.
Their list of products include: fire extinguishers, kitchen equipment,
fire suppression systems, alarm & detection systems, first aid &
safety equipment, exit & emergency lighting, and power washing equipment.
ABCO offers extensive repair and cleaning services for kitchen exhaust
systems and hoods including power washing.