<unk>  is the colloquial term to describe the air pressure differential between areas. Removing air from a space results in a pressure differential.<unk>  pressure is therefore limited by external air pressure. Even a perfect vacuum cannot suck with more pressure than is available in the surrounding environment.<unk> s can form on the sea, for example, when a ship founders. When the pressure in one g part of a system is reduced relative to another, the fluid in the higher pressure region will exert a force relative to the region of lowered pressure. Pressure reduction may be static, as in a piston and cylinder arrangement, or dynamic, as in the case of a vacuum cleaner when air flow results in a reduced pressure region. When animals breathe, the diaphragm and muscles around the rib cage cause a change of volume in the lungs. The increased volume of the chest cavity decreases the pressure inside, creating an imbalance with the ambient air pressure, resulting in<unk> .
Suction
Freeze spray
Mouthwash
Tao brush
Depot injection
Dressing 
Throat lozenge
Surgical mask