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Smoke Alarms Assignment In this CDA I will be explaining how smoke alarms work, there are two types of smoke alarms, Ionisation smoke detectors and Photoelectric smoke detectors

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In this CDA I will be explaining how smoke alarms work, there are two types of smoke alarms, Ionisation smoke detectors and Photoelectric smoke detectors, I will be explain what they both do and will compare them using a table to show the differences.  I will be also explaining what Americium is and Half-life is and what they do. Most people don’t know where and when smoke alarms are often used now a days and I’ll be explain that also.

Basic description:

Two basic types of smoke detectors are sold for residential use.

The photoelectric smoke detector: 

Uses an optical beam to search for smoke so when the smoke particles cloud the beam, a photoelectric cell senses the decrease in light intensity and triggers an alarm. This type of detector reacts most quickly to 
smoldering fires but no flame that release relatively large amounts of smoke.image00.jpgimage01.jpg

Ionisation smoke detector:

All smoke detectors have two basic parts: the sensors and the electronic horn that emits sound. These devices also require a power source, which is usually a 9-volt battery or 120-volt house current. Ionization-type detectors have an ionizing chamber with two electrically charged plates, and a minute amount of radioactive material is in between the plates. The radioactive material ionizes the air in the chamber, which results in current flow between plates.

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Number of alpha





Radiation with aluminium in the way





Number of beta





Number of gamma





% of alpha= 76/401 x100=25.4%

% of beta = 135/401 x 100= 33.6%

% of gamma = 162/401 x 100= 40.4%

Am 241 should be an alpha emitter

We did this to find out if there was more than one type of radiation coming out of the smoke alarms. The number of gamma radiation is the highest and there is least is alpha. I also found out that with paper in the way of radiation the number decreases

HOW TO MAKE IT MORE VALID: you can use accurate instruments which will make it more accurate.

TO MAKE IT MORE RELIABLE:  you will need to repeat the results with the same person

How long do smoke alarms last? What is the half-life of Am? Describe what manufacturers are trustworthy, are they valid? – The two types, their reliability, safety, cost:

Smoke alarms are cheap, easy to get hold of and, used properly, they really are lifesavers. There’s no excuse for not having one.

The photo-detector however, when there is smoke entering the chamber, the Smoke alarms are usually contained in areas of high risk from fire and smoke. They are warning device that detects smoke at the early stages of a fire. It sounds a piercing alarm to warn you.    

Many people that die in house fires are asleep at the time.

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Background radiation:

Background radiation resulting from cosmic rays and natural radioactivity is always present. Background radiation may also exist because of radioactive substances in other parts of a building (e.g., building material


The time in which the radioactivity usually associated with a particular isotope is reduced by half through radioactive decay

Ionising radiation:

Ionizing radiation is radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized.


A permanent change in the genetic material that may alter a trait or characteristic of an individual, or manifest as disease, and can be transmitted to offspring.


The radiation, including alpha particles, nucleons, electrons, and gamma rays, emitted by a radioactive substance.

Radon Gas: Radon is a naturally occurring gas produced when uranium breaks down into "radium".  The radium breaks further down to form a radioactive gas called radon













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