Densometers and porosimeters are used for measuring porosity, air permeability or air resistance of sheet-like or bulk materials. A porosimeter is used to measure the porous nature of a substance, including the total pore volume, surface area, and individual pore diameter. A densometer is used to measure the porosity of materials, or how permeable the material is to substances. Densometers and porosimeters are used to together to get a full picture of both the permeability and porosity of a particular substance, such as paper, fabric, woven materials, plastics, and other materials used as barriers or membranes.

Densometers and porosimeters are used to test the air permeability of a substance. Typically, a porosimeter is used to gauge air flow of a substance, where a densometer is used to test materials of lower permeability. For example, a porosimeter is used on breathable fabrics or absorbent felt where air flow is an important characteristic to their function. Densometers and porosimeters measure the flow differently as well. A densometer measures the time it takes to force a known volume of air through one square inch of material. A porosimeter measures the flow of air in cubic feet per minute that passes through a square foot of the material.

Densometers and porosimeters are used in industries that manufacture woven textiles and plastics, such as felt or other industrial fabrics. Densometers and porosimeters may also be used in the oil and gas industries to test the porosity of petroleum reservoirs. Some devices use mercury applied to the porous material in a high pressure environment to gauge the material’s porosity and permeability. A newer oil-filled pressure densometer is replacing the older model mercury densometer. A nuclear densometer is a special device used to test for moisture in soil and can produce readings through multiple layers of asphalt.