Environmental control systems and techniques for monitoring heat exchanger fouling are provided herein. In an embodiment, a technique for monitoring heat exchanger fouling includes providing a correlation of heat exchanger fouling to an operating variable. The correlation is programmed into a maintenance system that includes a processor that is adapted to receive data regarding the operating variable. The operating variable is chosen from inlet temperatures of input streams into the heat exchanger and outlet temperatures of output streams out of the heat exchanger, heat exchanger pressure drop, overall heat transfer coefficient value, speed of rotation of an air conditioning machine that includes the heat exchanger, and combinations thereof. Data regarding the operating variable is gathered via a sensor that is adapted to measure the operating variable. The measured operating variable is determined to correspond to excessive heat exchanger fouling in accordance with the correlation using the processor.
