Leakage rate
Tightness and mechanics- Notion of tightness and associated measures

A leak is characterized quantitatively by the quantity of fluid escaping from containment. It is expressed as :

• or by the mass that circulates per unit of time, the legal unit being the kilogramme per second (kg.s^-1); in practice, as this unit is often too large, sub-multiples such as the gramme per second (g.s^-1) or per hour (g.h^-1) are most often used;

• or by the volume escaping per unit time, expressed in cubic meters per second (m³.s^-1); here too, sub-multiples such as cubic centimeters per second (cm³.s^-1) or per hour (cm³.h^-1) are often used.

While with liquids, which are considered incompressible, pressure is irrelevant, this is not the case with gases. It is necessary to specify the reference pressure of the leaking gas (most often,...