Air leak testers judge leaks by pressurizing the inside (or outside) of sealed work by air and measuring the pressure change. When the master with no leak and work with leak are pressurized, the pressure of the work with leak will decrease generating pressure difference between the master and work. The leak is measured from this pressure difference. Generally, this differential pressure type air leak test is used for leak check. However, FUKUDA provides a lineup of products using a direct pressure type leak test or a flow meter according to the leak rate in addition to differential type leak testers. Furthermore, air is used as the medium for tests with these testers in which running cost is low and is environment friendly.