(ii) The cause of the fire is
(a) ascertained
(b) not ascertained
(c) yet to be ascertained
(d) unable to be ascertained
(iii) The fire was noticed
(a) before time
(b) on the exact time
(e) at the time of extinguishing
(d) at no point of time
В. Complete the following sentences with information from the text:
2.4.3
Answers
Answer:
i' : a
iii:' on the exact time
Explanation:
B=?
Explanation:
What is the fire tetrahedron?
To understand how to prevent fires, it is important to know how a fire can occur. Four elements must be present at the same time for a fire to take place:
Fuel or combustible material - something to burn, such as paper or wood.
Heat - to raise the material to its ignition (burning) temperature.
Oxygen - to sustain combustion (the fire).
Chemical reaction - the process of burning.
If you remove any of these four elements, the fire will not be able to burn.
What should I know about fighting fires?
Never fight a fire if:
You do not know what material is burning.
You do not know what type of fire extinguisher to use.
You do not know how to use the fire extinguisher.
The fire is spreading beyond the spot where it started.
Your instincts tell you not to.
If you are not confident about your ability to handle the situation (even if you are trained in fire fighting), or if you do not have the correct type of fire extinguisher, do not fight the fire. Pull the fire alarm, evacuate the area, and then call the fire department.
What are the different classes of fires?
Fires are grouped into classes which depend on the material or substance that is present.
Class A - Fires involving ordinary combustibles such as paper, wood, cloth, rubber, or plastics.
Class B - Fires involving flammable or combustible liquids, gases, oil, paints, or lacquer.
Class C - Fires involving energized (live) electrical equipment such as motors, appliances, or power tools.
Class D - Fires involving combustible metals such as magnesium, titanium, sodium, and potassium.
Class K - Fires involving combustible cooking oils, or fats in cooking appliances.
What are the different types of portable fire extinguishers?
To fight the different classes of fires, there are different types of fire extinguishers. Each has its own characteristics, capabilities, and limitations.
Three main types of portable fire extinguishers include:
Water extinguishers: Water extinguishers are filled about two-thirds with water and then pressurized with air. When used for Class A fires, these extinguishers remove the heat from the burning materials.
Do not use water to extinguish an electrical fire. Water is a good conductor and can increase the possibility of electrocution.
Do not use water to extinguish flammable liquid or cooking oil fires. Water is ineffective as it helps to spread the liquid and the fire.
Carbon Dioxide (CO2) extinguishers: The extinguishing media is pressurized CO2. When used for Class B and C fires, the CO2 covers the fuel by blanketing it, and stops the reaction at the surface by displacing oxygen. Be thorough when using a CO2 extinguisher. It has a moderate spray range and last only 10 to 30 seconds. A hard horn attached to the end of the spray tube helps to contain and aim the spray at the target area.
Do not use CO2 extinguishers in confined spaces as CO2 can displace the oxygen in the air, making breathing difficult. Only use in a confined space if workers have appropriate respiratory protection.
Do not use CO2 extinguishers for Class A fires because the fire may continue to smolder and re-ignite after the CO2 disperses.
Dry Chemical extinguishers: Dry chemical extinguishers are the most common and available in few types. These extinguishers will be marked for the classes they are designed to extinguish (e.g., ABC type extinguisher will put out Class A, B and C fires). The extinguishers discharge a blanket of fine powder which creates a break between the fuel and the oxygen in the air. The powder also works to break the chemical reaction. Be accurate when using as they have a short to moderate spray range and last only 10 to 25 seconds.
Be cautious of the residue after using dry chemical extinguishers. The residue can damage motors, computers and other electrical equipment.
Below is a summary of these and other common extinguishers.
Extinguisher Comparison TableExtinguisherClassRangeEmptiesOtherWaterALong60 secFights re-ignitionCO2B and CShort10-20 secMay make breathing difficult in enclosed areasDry ChemicalB and C
Some AModerate10-25 secLeaves residueLiquid GasB and C
Some AShort10 secMay make breathing difficult in enclosed areasChemical FoamA and BModerate10-30 secLeaves residueBucket of Sand / Dry PowderD Check with your supervisor regarding equipment for Class D fire fightingWet ChemicalK Prevents re-ignition
How will portable fire extinguishers be marked?
Portable fire extinguisher may use the following markings to indicate which class of fire they are designed to fight. These symbols are recommended by the National Fire Protection Association (NFPA) in the USA. The symbols may be shown using colours.

What you should know when using a portable fire extinguisher?
Always:
Be sure that you are trained to use a fire extinguisher before you try to fight a fire.
Know what type (class) of material is burning.
Use the correct fire extinguisher type to fight the fire.
Remember, if you feel that you cannot safely extinguish t