Which of the following is NOT a type of BAK-14 heater?

The BAK-14 heater is a specific infrared heater used in airfield and taxiway applications for ice and snow melting purposes. The types of BAK-14 heaters are designed for various configurations and placements related to airfield infrastructure.

The option identifying the upper chamber heater is correct as this type does not exist within the recognized classifications of BAK-14 heaters. Instead, the BAK-14 heater types include configurations that focus on efficient heating where it is needed for effective melting of ice or snow.

Box heaters, end trough heaters, and cross runway drain heaters align with known BAK-14 heater designs and are tailored for specific locations within airstrips where heated air needs to be focused to prevent the buildup of ice and snow. Each of these types serves a defined purpose, optimizing the melting of hazardous conditions around runways and taxiways.

Understanding this classification helps in recognizing that the BAK-14 heater system is methodically designed with varied types to meet the functional demands of airport operations effectively, while the upper chamber heater does not fit this framework.