.The most obvious form of humidification equipment is the spray chamber. Here, the contacting liquid is sprayed as a mist into the gas stream. Gas velocity is kept low so that the contact time is high so that there will be only small amount of liquid physically entrained in the gas stream. These units are usually restricted to the small-scale operations and are frequently used in humidity control of a room or plant where either humidification or dehumidification of the inlet air is required.