What are the three essential conditions for combustion to occur?

The correct answer identifies the three essential conditions for combustion as oxidizer, fuel, and heat. Combustion is a chemical reaction that occurs when a fuel reacts rapidly with an oxidizer, typically oxygen, producing heat and light.

An oxidizer is essential because it provides the necessary oxygen that combines with the fuel during the combustion process. The fuel is the substance that burns, and includes various hydrocarbons such as natural gas, gasoline, wood, etc. Heat serves as the initiating energy that starts the combustion reaction and sustains it. Without all three components — an appropriate fuel, the presence of an oxidizer, and sufficient heat to initiate and sustain the reaction — combustion cannot take place.

Understanding these three elements is crucial for designing efficient combustion systems in HVAC applications and ensures safe operation. Other options provided may mention related factors but do not accurately encapsulate the conditions required for combustion.