The removal or addition of air volume to the space is the air change rate
The rate of air change is positive when air volume is added to the space and the rate of air change is negative when air volume is removed from the space.
The standard built home has a 0.5 to 1 of air change rate.
The rate of air change is dependent on the building (how the building form)
Stress analysis tells us the deformation of objects occurs at specific points where stress or the internal forces reach points where the material can no longer resist or reach a point of equilibrium.
Brittle material have a far lower breaking point then say metals.