Smoke Detectors: A Rescuer Invention
Introduction -
Residential fires have become a serious problem throughout the world.Cigarettes are one of the main cause of accidental fires in the residential building .In addition to this some of the fixed and portable heating equipment adds the fire in the building like kerosene heaters ,stoves, electric cooking stoves and gas .
Early warning systems –
There are two types of residential fire detection systems: Heat and Smoke detectors. Heat detectors as name suggests detects only heat from the fire and aware us from the fire while smoke detector not only detects smoke but also sounds an alaram so that one can conscious from fire and always precede heat detectors.
Smoke detectors –
These are the important home safety devices. It consists of a sensing chamber, alaram sounding device and a battery (Mostly 9 volts alkaline batteries) to supply a power.
History -
The development of these life-saving domestic devices began in 1902 by George Andrew Darby who was an electrical engineer .Initially these devices was actually a heat detector operated by electrically and indicates the rise in temperature in the residential buildings where they were fitted for safety. Alarm sounds due to the falling of one plate on another when temperature rose beyond the limits; but as era passed inventions are made and inventors found the devices like LED(light emitting diode ) and sensors simply to detect the smoke and becomes named as smoke detectors today.
Types of smoke detectors –
There are two types of smoke detectors
1) Ionization smoke detector
2) Photoelectric smoke detector
1) Ionization smoke detector -
This type of smoke detector used a radioactive source (generally americium-241
An alpha-emitting radionuclide) to ionize the air within the sensing chamber so as to detect the smoke.
Construction –
The ionization chamber consists of two metal plates separated by a small distance in order to generate a voltage between them. One of the plate carries cation (i.e. negative charge) and anions are on the another plate (i.e. positive charge).Radioactive source of ionizing radiation (americium 241) simple emits alpha particles that are responsible for ionizing the air molecules – made up of hydrogen and oxygen atoms between the two plates by simply jerking the electrons from the molecule; as alpha particles are heavy and big than the electrons. Consequently free electrons are attracted on the plate having negative charge and hydrogen and oxygen atoms are drop on positive charged plate.
Fig –
Fig- a shows smoke free chamber with positive and negative charged on the two metal plates
.
Fig- b shows how smoke particles interact with ions in the ionization chamber thereby neutralize the ions and decrease an electric current between the chambers.
Working –
When smoke enters in the ionization chamber, current in the chamber interrupted due to appending the smoke particles to the positive and negative charged ions thereby neutralize them. Now as electricity drops between the two plates in the ionization chamber, automatically fire alaram triggered and it elicits the sound.
During operation a chemical reaction takes place between americium 241 and alpha particles.
O2 +He (+2) _____ O2 (+1) + e (-1) +He (2)3
Advantages –
a) They are inexpensive
b) Quick react with fire flames
c) They are highly reliable
d) Fast in operation simple with easy to install
2) Photoelectric smoke detector
They work on the principle of dispersed or mirror light to indicate the presence of visual smoke.
Construction –
Basically it consist of T shape chamber (a horizontal bar) with LED (Light-emitting diode) and a photocell i.e. light and sensor mechanism. Light emitting diode emits the light in the horizontal bar .Sensor i.e. photocell fitted at the bottom of the mechanism and is activate when comes in contact with the light. Generally light and sensor are intersected at right angle to each other.
Working -
When there is no smoke inside the chamber, the chamber is dark. I.e. light from light emitting diode travels in straight line without striking the sensor situated at the bottom of the mechanism. When a smoke particle enters in the chamber, these particles replicate some of the light in all directions. Due to this some of the light falls on the photocell i.e. sensor and activate the sensor. The stimulated sensor now generates the current and the current simply set off the alaram in the smoke detector.
Advantages –
1) Ability to detect small and invisible particles
2) Better at sensing smoky fires.
Comparison between ionization smoke detector and photoelectric smoke Dector –
Actually both types of smoke detectors are designed to detect to sense the smoke present in the air. Photoelectric smoke detectors sense the perceptible smoke particles (like a cigarette) and become faster; while in case of ionization smoke detector it detects the indistinguishable particles (like fabric particles).If fires start without flame then we need to use photoelectric smoke detector since it having a good detection time on the other hand if fire contains a observable flame then in such a case ionization detector is appropriate. So therefore both the smoke detectors are useful since both will warn us in case of fires.
Impact of Technology –
Personally, smoke detectors have a positive impact on me. When I was a student of higher secondary school i.e. before seven years I heard the word smoke detector due to one of the incident in our chemistry lab, ever before I had never heard what smoke alarm is and how it works. When we were doing experiment in the lab unfortunately our store room subjected to fire due to some means which contains hazardous chemicals but as lab had already smoke alarm systems so we all aware from the fire and within five minutes we quench the fire and liberate from the incident.
From that event I am really influenced by smoke detector and familiar how smoke detector warns us when fire breaks out and defenses us against fire. Today the installation cost of smoke alarms has less than $40 for the entire house and it is contemptible and reliable since alarm could save our own life and those whom we loved by providing the chance to break out.
Globally, smoke detectors play a major role. Today Residential building, motel, offices, school buildings, manufacturing firms have benefited from smoke detectors because these fire detecting devices not only saves lives of millions of people but also protects property ,job and services of the society. Every year thousands of peoples are died, injured with damage of public and private possessions due to fire, this problem now overcome by smoke detectors since the new smoke detectors react automatically to detect the fires more quickly because of their improved sensitivity and flexibility.
Economically smoke detectors are beneficial tools for the society. Fires in the buildings are not happens regularly but if we are aware of the fire we reduces the total expenditure due to the fire including direct and indirect cost of fire losses as well as public and private fire security cost .
Pollution which is hazardous to human being is eliminated by smoke detector technology. If fire starts in the building it allows some physical and chemical processes which are due to the product of combustions having high temperature and flammability properties of the materials.
Fire creates stressful situations in a human being. Since if a building is suffering from the fire then it is necessary to leave the building as early as possible for and one need to call the fire brigade to extinguish the fire. This is an emergency situation and anything happened. This problem is reduced by simply smoke detector technology since as alarm sounds; peoples in the buildings without doing anything simply leave the building.
Smoking problem somewhat reduced by smoke detectors since at least in the residential building or around the area where smoke detector installed, smokers avoid smoking thereby reduces the chances of disease like cancer, heart disease and emphysema.
Installing a smoke detector in the residential building could have saved the life of millions of peoples with prevention of injuries and eliminated millions of dollars in a public and private property loss due to the fire.
There is nothing to say about smoke detectors if it is harmful except the people with hearing loss because smoke alarms are useless for the people who are deaf and hard to hear something.
The best example why we need to install the smoke detector technology is ‘leakage of MIC (Methylisocyanate) gas at Bhopal,Madhya Pradesh, India’ which is the greatest industrial disaster in the history of India. About 40 metric tones of MIC gas leaked results in high temperature and pressure .As a result of this accident 3000 people died and people injured range from 2, 00,000 to 6,00,000. With thousands of people still suffering. All this happened was due to the absence of safety devices because none of the safety systems designed to contain such a leak were operational, allowing the gas to spread throughout the city of Bhopal .If the factory had installed smoke detector system in their department then the technology sense the gas and not only it saves the lives of people but also prevent the factory from closed. (http://www.corrosion-doctors.org/Pollution/bhopal.htm)
Conclusion –
Smoke detector technology not only protects the society from fire but also saves public and private property from burning thereby creating pollution free environment.
References
1. How smoke detector works by Marshall Brain from
2. Smoke detector and radiation, Ionization technology from
3. Smoke detector and radiation, Ionization technology from
4. Smoke detector, a savior invention from
5. Smoke detector and radiation, phoelectric technology from
6. Bhopal Accident from