The ability of a gas, or air, to diffuse through a material when the pressure of each side of the material is different, i.e. high pressure or a vacuum. Porous materials will allow the gas to pass through quickly. Materials with low gas permeability are often used as barriers in food packaging. Gas permeability is usually given in the units of milliliters per square meter per day (ml/m2.d). This indicates the volume of gas that will pass through a square meter of the test material in one day. The thickness of the test material must be specified. A typical test thickness is 1 mil (1 thousandths of an inch thick). An equivalent measurement is cc/m2.d, where one cubic centimeter (cc) is equal to one milliliter. The permeability of gases (air, oxygen, nitrogen, etc.) is dependent on the porosity of a substance, while water vapor transmission is dependent on the absorption of water into the material.
Synonyms and Related Terms
Gaspermeabilität (Deut.); perméabilité aux gaz (Fr.); permeabilidade aos gases (Port.); air permeability; oxygen permeability
ASTM test procedure D737
Sources Checked for Data in Record
- The Dictionary of Paper, American Paper Institute, New York, Fourth Edition, 1980
- Fairchild's Dictionary of Textiles, Phyllis G.Tortora, Robert S. Merkel (eds.), Fairchild Publications, New York City, 7th edition, 1996
- Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982