Which of the following is NOT a component found in a gas appliance?

In gas appliances, components are specifically designed to facilitate the efficient combustion of fuel and the transfer of heat. A burner, gas valve, and heat exchanger are integral parts of most gas appliances.

The burner is pivotal because it mixes gas with air to create a flame, which is essential for combustion. The gas valve controls the flow of gas to the burner, ensuring that the right amount is delivered for safe and efficient operation. The heat exchanger is responsible for transferring heat from the combustion gases to the air or water, depending on the appliance's function, such as in heating applications.

In contrast, a fuel injector is not a standard component in typical gas appliances. Fuel injectors are more commonly associated with liquid fuel systems or specific types of combustion engines, such as those found in automobiles, where precise fuel delivery is critical for performance. Gas appliances primarily rely on burners rather than injectors to manage gas flow and combustion.

Therefore, the absence of a fuel injector in the list of common components found in gas appliances makes it the correct answer to the question.