An underwater seal chest drainage system is used to restore proper air pressure to the lungs, re-inflate a collapsed lung as well as remove blood and other fluids. The system is a two-chambered or three-chambered plastic unit with vertical columns bringing measurements marked in milliliters. The thoracic drainage devices cover a wide range and have evolved considerably since their introduction. The basic design principle of these systems has been the avoidance of air entrance in the pleural cavity during the various phases of the respiratory cycle and continuous drainage of air and fluid from the pleural cavity. A key issue in the successful treatment of patients is the understanding of how these systems function. The application and development was based on the original one-bottle system.