TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The apparatus further includes heaters for heating the gas between the humidification chamber and the evaporation chambers, before the gas inlet, and/or after the gas outlet. It also includes temperature sensors at the heater outlet, and temperature controllers for controlling heaters. The elements in the humidification chamber can be demister pads, baffles, perforated baffles, trays, or packing. The water inlet flow controller controls a device, such as control valve or metering pump. The evaporator chamber port provides restricted fluid communication between the evaporator chamber and the gas humidifying chamber, a small opening to prevent passage of the gas into the evaporator chamber during use and an orifice. A humidistat is also included to provide feedback to a humidification controller having an output to an oscillator. The ultrasonic mister comprises a transducer having a metal disk that vibrates in response to an electrical signal from the oscillator. The transducer is submerged in the evaporator chamber, and vibration produces minute droplets of water. The apparatus also includes water vapor conveyance device selected from piping or tubing and side ports in the humidifying chamber in fluid communication with the evaporator chamber.    TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Method: The method further involves monitoring the performance of the fuel cell while changing the flow rate of the water in proportion to the flow rate of the reactant gas stream; monitoring the temperature of the water vapor, and maintaining the temperature of the water vapor at a set point temperature; monitoring the performance of the fuel cell while changing the set point temperature of the humidified reactant gas stream; monitoring the evaporation rate of the water in the evaporation chamber; and adjusting the amount of water supplied to the evaporation chamber based on the evaporation rate of water in the evaporation chamber.