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

CDA

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.

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. Any smoke that comes into the chamber will interrupt the ion flow and cause a reduction in current flow that sets off the alarm.

The differences between photoelectric and ionization smoke detectors are they both detect smoke differently, like for example the photoelectric smoke detectors 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 the alarm, as the ionisation smoke detector detects smoke when the it reaches its chamber, making it interrupt the ion flow it causes a reduction in current flow that will set off the alarm.

They also use different power supplies such as, batteries or AC currents. Some also have a interconnectivity, which triggers all alarms if one alarm is triggered, warning every one on each level on the house.

O2 + He+2 O2+1 + e- 1 + He+2

This is the equation for smoke alarms and the equation says that oxygen and alpha particles make a positive charge. But when the smoke gets it, it doesn’t do that and the alarms go off, the radioactive material ionizes the air in the chamber, which results in current flow between plates. Any smoke that comes into the chamber will interrupt the ion flow and cause a reduction in current flow that sets off the alarm. Ionization models are best suited for rooms that contain highly combustible materials that can create flaming fires. These types of materials include flammable liquids, newspapers, and paint cleaning solutions. Photoelectric models are best suited for living rooms, bedrooms and kitchens. This is because these rooms often contain large pieces of furniture, such as sofas, chairs, mattresses, counter tops, etc. which will burn slowly and create more smouldering smoke than flames.

Analysis

Where and when are smoke alarms used?

Smoke alarms are often used in homes, offices, most likely everywhere, they are mainly there for in case of fire, like for example if something has over cooked in your kitchen it would maybe start a light or in your living room with the electronic cables might melt due to heat and produce a fire, then the smoke alarms would sense the smoke and start the horn, trying to get the everyone’s attention in the house. So they can mainly do something about it for example by putting it ...

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Analysis

Where and when are smoke alarms used?

Conclusions about uses of smoke alarms:

Their main job is to sense smoke in how ever way the both types do and give out a loud signal helping people to escape out of their house, the uses of smoke alarms has continued to increase but a substantial proportion of British homes still do not have some alarms. Homes at greatest risk of residential fire are the least likely to have an alarm. Health professionals are able to increase smoke alarm that will be used among families with children, by counselling families with benefits of smoke alarms. Even though smoke alarms are cheap and easy to buy as well as fitting it . but there are also smoke negative issues such as they a giving small amounts of alpha radiation and high amounts of beta radiation. This is damaging us little by little but some may say that it is saving our lives and its worth it. Radiation is a high concern and smoke alarms are adding on to it which is causing our cells to mutate.

Americium Activity:

% 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. A smoke alarm will wake you up and give you time to escape.

Smoke alarms cost from as little as £5.00. They are available for DIY stores, electrical shops, supermarkets and high street shops.

Living in rented accommodation? Landlords are not legally required to fit smoke alarms your safety is your own responsibility!

Long-life smoke alarms have been designed to use lithium batteries where the battery life is predicted to last a very good 10 years with the normal battery drain of ionization type smoke alarms. The smoke alarms are specially designed to provide a low battery audible signal as the battery charge is reduced to reasonable low level that may make the smoke alarm inoperable.

Half-life of smoke alarms

Smoke alarms can have a half life cycle up to 20 years if design and instillation advice is followed and annual maintenance is performed.

For example,

Uranium -234 gives out alpha radiation which has a half life of 250 000 years. This would be good for smoke alarms because you can guarantee you would get your money’s worth and if there is a fire you can trust that it will work. However, radon-220 would be a really bad things to use for smoke alarms, this also gives out alpha radiation but only has a half life of 56 seconds, which would be really bad because if there was a fire the smoke alarm couldn’t let you know because it would have worn out.
How to get rid of a smoke alarm
The best way of getting rid of smoke alarms is to put them in a normal rubbish bin; this is OK because the concentration of radioactivity in soils is about the same as 10 or more smoke alarms. When more than 10, smoke alarms are to be disposed of. However, they must be treated as radioactive waste.
How do smoke alarms work
the detector consists of a very small quantity of a radioactive source. This gives out tiny particles due to radioactivity. The particles collide with air molecules in the chamber. This produces ions. The ions move to the other charged plate. This flow of ions causes a small electric current in the circuit. When smoke particles enter the chamber, they collide with the ions, this slows them down. So the current decreases, a loud noise then sounds.

Applications and implications of science

What are people’s worries about smoke alarms?

They have a worry that they will put this object with radio activity in their home. It could also emit radiation and kill everyone. So people are cautious about getting them.

A general concern is that only one person will hear the alarm and must alert all others in the house who must follow a prior plan to escape (out windows using rope ladders, etc.) to avoid the flames. Everyone should meet at an assigned location so that no one races back inside to rescue someone who has already escaped.

Table for and against using smoke alarms:

How much americium is used in smoke alarms and how much would be left after 10 years?

The amount of americium-241 used is less than 1 . This enables the smoke detector to be able to detect smoke while also not causing diseases among human beings who come into close vicinity to it on regular basis.

Smoke alarms each contain 30,000 Bq. The radioactivity in ionising detectors is a film coated with Americium 241, a relatively long-lived and very active alpha emitter (half life 432.2 years, 1167 million Bq per milligram).

Disposing smoke alarms

Disposing smoke alarms can still be dangerous; this is because after they have been disposed of, it will still have radiation being emitted for 10 more years. And if this catches fire then radiation will be let off into the atmosphere

In conclusion:

Although smoke alarms save many lives and are easy and cheap and are easily fitted there are still many things wrong with them.

Although there are small amounts of alpha radiation, there is a high amount of beta radiation. Although they are very useful they still damage us as people by mutating our cells which could lead into getting cancer or seriously ill. But if you do not have smoke alarms there is more of a chance of you not knowing that there is a fire and when you do realise it is too late. They are easy to dispose but they will still keep letting off radiation 10 years after being disposed of.

Glossary:

Alpha particles:

A positively charged particle that consists of two protons and two neutrons bound together. It is emitted by an atomic nucleus undergoing radioactive decay and is identical to the nucleus of a helium atom. Because of their relatively large mass, alpha particles are the slowest and least penetrating forms of nuclear radiation. They can be stopped by a piece of paper.

Beta particles

High-speed electron or positron, usually emitted by an atomic nucleus undergoing radioactive decay. Beta particles are given off naturally by decaying neutrons in radioactive atoms and can be created in particle accelerators. Beta particles have greater speed and penetrating power than alpha particles but can be stopped by a sheet of aluminium that is 2 to 3 mm thick

Gamma rays

Light with the shortest wavelengths and the highest energies and frequencies in the electromagnetic spectrum; also called gamma radiation. Gamma rays are produced by violent events such as supernova explosions. They are also produced by the decay of radioactive materials. Gamma rays can kill living cells, so it is good that Earth's atmosphere can stop them. Gamma radiation is used in medicine to kill cancer cells.

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

Half-life:

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.

Mutation

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.

Radioactivity

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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