Which of the following is NOT a common air supply system on rescue vehicles?

Electric air pumps are not typically used as air supply systems on rescue vehicles. The standard systems employed include breathing air compressors and cascade systems. Breathing air compressors are designed to fill air cylinders with breathable air for fire and rescue operations, ensuring that responders have access to the necessary air supply. Cascade systems are used for storing high-pressure air that can be used to refill smaller air tanks efficiently.

In contrast, nonbreathing air compressors are also uncommon in rescue operations, as they do not provide breathable air suitable for personnel in hazardous environments. The role of electric air pumps usually pertains to inflating items rather than supplying air for breathing in critical rescue situations, which is why they do not fit within the typical setup for air supply systems on rescue vehicles.