Venturi 1 : A constricted portion of a pipe or tube which increases water velocity, thus momentarily reducing its pressure. It is in this reduced pressure area that Foam Liquid is introduced in many types of proportioning equipment
National Foam, A Firefighter's Guide to Foam (Foam Glossary), Kidde Fire Fighting, Exton, PA, USA 2008. http://www.zurichservices.com/zsc/pptlibrary.nsf/c e835d312fec922c862568010078a415/1808b7dc16b70efc06 25687f001364cf/$FILE/Firefighters%20Guide%20to%20F oam%20(National%20Foam).pdf, (Fom - Amer) {143}