Hydrostatic Pressure (AATCC 127)
Test measures resistance of material to the penetration of water under hydrostatic pressure. Hydrostatic pressure is the force distributed over an area exerted by water. The higher the test result (expressed in mm), the greater the resistance to fluids passing through the material under pressure.
Note: The hydrostatic rating of a material is inverse to air permeability, thus the greater the hydrostatic rating (mm), the less the air permeability and comfort of the coat.