Which one of the following is NOT a main component of an air brake system?

The main components of an air brake system include the brake chambers, air tanks, and air compressor. Brake chambers are responsible for converting the pressure of the compressed air into mechanical force to apply the brakes. Air tanks store the compressed air needed for braking, and the air compressor generates the compressed air and maintains pressure in the system.

While the brake pedals are essential for controlling the vehicle's braking system, they are not considered a main component of the air brake system itself. Instead, they are part of the overall vehicle control system, allowing the driver to engage the air brake system when needed. Thus, while important for operation, brake pedals do not fall under the category of the main components that specifically define how the air brakes function.