Casualty Actuarial Society (CAS) Practice Exam

What is a key component needed to start a destructive fire?

1. Excess fuel only

2. An uninterrupted chain reaction

3. A source of oxygen

4. A spark of electricity

The correct answer is: A source of oxygen

To initiate a destructive fire, a source of oxygen is essential. Oxygen is a critical component of the fire triangle, which includes fuel, heat, and oxygen. In a fire, oxygen facilitates the chemical reaction that occurs when fuel combusts. Without adequate oxygen, a fire cannot sustain itself, regardless of the presence of other elements like fuel or heat. While fuel and heat are important, the presence of oxygen is what supports combustion. The atmosphere typically provides enough oxygen for most fires, as it contains around 21% oxygen. A fire will not start or will be extinguished if there is a lack of oxygen, regardless of the amount of fuel or heat available. Other answers may mention aspects like fuel or a spark; however, these elements cannot initiate a fire without the necessary oxygen. In summary, oxygen is integral to the combustion process, making it a crucial component needed to start a destructive fire.