Suction Explained

A quick overview of the science at work

  • Vacuum
  • Atmospheric Pressure
  • High Pressure
  • Boyle's Law
  • Creating Vacuum
  • Max Vacuum

What is vacuum?

Vacuum is the absence of matter. 

In space there are no molecules (or really very few) to exert pressure on an object.

Earth's atmosphere is mostly comprised of nitrogen and oxygen. The weight of these molecules exerts a force on everything below it. This weight is what creates the atmospheric pressure.

Atmospheric Pressure

Atmospheric Pressure?

Above each of us is a column of molecules that extends 62 miles into space. These molecules exert 14.7lbs of pressure per square inch (14.7 psi) on you all day, everyday. 
High Pressure

High Pressure

Adding matter into an enclosed environment increases the pressure. 

This is exactly what happens when you inflate a tire. The pressure inside the tire exceeds the pressure outside (atmospheric pressure).

Boyle's Law

Boyle's Law teaches us that matter in an enclosed environment will move from an area of high pressure to lower pressure until an equilibrium is reached.

This is the principle we use to create suction.


Creating Vacuum

Vacuum is created when molecules are pumped out of an enclosed area, such as a suction canister. This vacuum is commonly referred to as negative pressure because it is less than the atmospheric pressure we have grown accustomed to.

When the suction tubing is unclamped, molecules from the surrounding environment rush through the tubing into the canister to equalize the pressure (Boyle's Law).

Max Vacuum

The lower the pressure in the vacuum canister the stronger the vacuum will be. Conversly the higher the atmospheric pressure, the stronger the vacuum will be.

The theroretical maximum suction strength that nature allows is equal to the atmospheric pressure. (760mmHg at sea level)

Medela's Dominant Flex removes up to 94% of atmospheric pressure!

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