Suction

Suction is the process of drawing a substance into a region of lower pressure, typically by a device such as a pump or by the action of surface tension in a suction cup. In gases or liquids, suction involves creating a negative gauge or absolute pressure relative to the surrounding environment, so that fluid flows toward the area of lower pressure. The term is used both for mechanical systems and for everyday phenomena like a suction cup sticking to a surface.

The underlying mechanism is a pressure differential. A pump or other means lowers the pressure in a vessel; the surrounding fluid moves toward that lower pressure to equalize the difference. The rate of flow depends on the magnitude of the pressure difference, the resistance of the pathway, and the properties of the fluid, such as viscosity. In open systems, suction can also be created by rapid movement of air, as in a venturi or in a siphon.

Applications: Medical suction devices remove secretions, blood, or other fluids from airways or wounds. Suction catheters, Yankauer tips, and wound vacuum systems rely on controlled negative pressure. Industrial uses include vacuum cleaners, material handling, and laboratory filtration. Suction cups use atmospheric pressure around the cup edge to create a holding force when a partial vacuum is formed beneath the cup against a smooth surface.

Safety and considerations: improper suction can cause tissue trauma or barotrauma; devices include regulators, valves, and filters to maintain safe pressures and prevent contamination. Equipment must be compatible with the medium and environment, and maintenance is important to avoid leaks or loss of suction.