Login or register (free and only takes a few minutes) to participate in this question.
You will also have access to many other tools and opportunities designed for those who have language-related jobs (or are passionate about them). Participation is free and the site has a strict confidentiality policy.
Densometers are the accepted standard for measuring the porosity, air-permeability or air-resistance of sheet-like materials such as papers, wovens, plastics and membranes. All Densometers measure the time required for a given volume of air (25cc to 400cc) to flow through a standard area of material being tested under light uniform pressure.
So it's obvious from the definition that the unit is seconds per square millimeter (metric) or second per square inch (English) - s/mm2 or s/in2