Construction Equipment and Tools MCQ with answer and solution

Concept

Classification of fires and selection of appropriate fire extinguishing media, specifically for electrical installations.

Step-by-step solution

1. Identify the type of fire mentioned: electrical fire involving live electrical equipment. 2. Recall the classes of fires and suitable extinguishers: Water and foam extinguishers conduct electricity and can cause fatal shocks. Dry powder can be used, but it leaves a corrosive residue that damages sensitive electrical components. 3. Carbon dioxide (CO2) displaces oxygen, does not conduct electricity, and leaves no harmful residue, making it the ideal choice for electrical fires.

Explanation

For electrical fires (Class C fires) on construction sites, carbon dioxide (CO2) extinguishers are preferred because CO2 is a non-conductor of electricity and leaves no residue, preventing further damage to equipment and avoiding electrical shock hazards.

Why the other options are wrong

A: Water extinguishers conduct electricity and create a severe electrocution hazard. B: Foam extinguishers contain water and are conductive, making them unsafe for electrical fires. D: While dry powder can extinguish electrical fires, it leaves a damaging residue and is typically secondary to CO2 for sensitive equipment.

Shortcut

Remember 'C for CO2 and C for Current/Electrical fires'.

Common mistake

Using water or foam extinguishers on electrical fires, which poses a severe risk of electrocution.