Breathing circuits are systems used in medical settings to deliver oxygen and remove carbon dioxide from a patient's lungs. They are commonly found in devices like ventilators, which assist patients who cannot breathe adequately on their own. The circuit typically includes a series of tubes, valves, and filters that ensure a continuous flow of air. These circuits can be classified into two main types: open circuits and closed circuits. Open circuits allow exhaled air to escape into the environment, while closed circuits recycle exhaled air, often using a carbon dioxide absorber to purify it. Proper functioning of breathing circuits is crucial for patient safety and effective respiratory support.