A chest drainage canister device is typically used to drain chest tube contents (air, blood, effusions). There are generally three chambers. The first chamber is a collecting chamber. The second is the "water seal" chamber which acts as a one way valve. Air bubbling through the water seal chamber is usual when the patient coughs or exhales but may indicate, if continual, a pleural or system leak that should be evaluated critically. It can also indicate a leak of air from the lung. The third chamber is the suction control chamber. The height of the water in this chamber determines the negative pressure of the system. Bubbling should be kept a gentle bubble to limit evaporating the fluid. Increased wall suction does not increase the negative pressure of the system. Newer systems are designed not to need the water seal chamber, so there is not a collumn of water that can spill and mix with blood, mandating the replacement of the canister. Even newer systems are small and portable so the patient can be sent home for drainage if indicated.