Reach-In Chambers vary in size from 0.5 cubic feet to more than 70 cubic feet. Virtually any environment can be created in these chambers. Temperature, humidity, altitude, rain, solar and vibration are just a few. The environment to be conditioned is controlled at a targeted dew point temperature and then reheated to a specified air temperature. This methodology follows a proven technique that maintaining a constant dew point and air temperature will produce a very constant relative humidity. A portion of the air returning from the conditioned area is directed through a water spray area, the temperature of which is very closely controlled. The temperature of the water spray is adjusted to maintain the dew point temperature of the targeted condition. As the air passes through the water spray, it is cooled down to the temperature of the water and approaches saturation at that temperature. The air then leaves the spray chamber through a mist eliminator, which removes any free droplets of water and is next mixed with air that has by-passed the spray area. After passing over an electric heater, to warm the air back to the desired dry bulb temperature, the air is returned to the conditioned space. Utilizing the above method, a very precise humidity control is achieved.