Answer :

CO₂ portable fire extinguishers are primarily used for Class B and C fires, which involve flammable liquids and electrical appliances respectively. CO₂ extinguishers work by blocking oxygen and removing heat from the fire. They're not recommended for Class A fires, which involve combustible materials like wood or paper.

CO₂ portable fire extinguishers are primarily used for class B and C fires. Class B fires involve inflammable liquids such as gasoline, oil, and oil-based paints. Class C fires are the ones involving electrical appliances and wiring like computers and fuse boxes.

The reason why CO₂ extinguishers are preferred for these classes of fires is due to their ability to smother the fire by blocking oxygen and removing heat with a very cold discharge. CO₂ extinguishers are considered as clean agents as they do not leave any harmful residues after use.

However, they are not suitable for class A fires, which involve common combustibles like wood or paper, as CO₂ can potentially scatter the material and spread the fire.

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Final answer:

CO₂fire extinguishers are primarily used for Class B (flammable liquids) and Class C (electrical equipment) fires. They work by displacing oxygen, suffocating the fire but are not effective for fires involving magnesium. Their functionality is temperature-sensitive, and no liquid CO₂exists in the extinguisher when temperatures exceed 31 °C.

Explanation:

CO₂ portable fire extinguishers are primarily used for Class B and Class C fires. Class B fires are those which are caused by flammable liquids or materials that liquefy such as petrol, oil, paint, some waxes & plastics. Moreover, Class C fires are associated with electrical equipment. CO₂fire extinguishers are preferred for these types of fires since they work by displacing oxygen, thus suffocating the fire. An important point to note is that they are not effective on fires involving magnesium, which can chemically react with CO₂.

Furthermore, the functionality of a CO₂ extinguisher is temperature-dependent. On a cool day, the temperature of the CO₂is below its critical temperature of 31 °C; hence liquid CO₂ exists in the extinguisher. However, on a hot day, when the temperature exceeds 31 °C, no amount of pressure can liquefy CO₂, resulting in no liquid CO₂in the extinguisher.

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