An aircraft fuel tank ventilation system, comprising a desiccative dehumidifying device including a desiccant medium disposed in flow communication between a vent open to the atmosphere and a fuel tank, and a microwave energy transmitter for energizing liquid water in the desiccant medium to facilitate regeneration of the medium. Also, a method of regenerating a desiccant medium of a dehumidifying device of an aircraft fuel tank ventilation system, the method comprising directing air through the desiccant medium, and transmitting microwave energy into the desiccant medium for energizing liquid water in the desiccant medium to facilitate regeneration of the medium.