The scientific law that describes the relationship between air pressure and volume is Boyle's Law.

Boyle's Law states:

* At a constant temperature, the volume of a given mass of an ideal gas is inversely proportional to its absolute pressure.

This means that if you increase the pressure on a gas, its volume will decrease proportionally. Conversely, if you decrease the pressure, the volume will increase.

Mathematically, this is represented as:

* P₁V₁ = P₂V₂

Where:

* P₁ = Initial pressure

* V₁ = Initial volume

* P₂ = Final pressure

* V₂ = Final volume