This study investigated the ability of an online pressure differential leak detector to assess the quality of seals in 1775 ml polyethylene terephthalate (PET) bottles. Results of these tests showed that: (1) the minimum leak detection was 20 mu m in diameter; (2) no false positives or negatives were produced during normal testing; (3) the leak tester was capable of detecting seals made with sub-optimum sealing conditions and (4) the headspace analysis showed that the leak tester will not produce false positives results if the headspace measurement is between 3 and 5 cm. However, headspace measurements above and below this range could cause the tester to produce incorrect results. The results of this study can be used to verify the efficiency of similar non-destructive leak testers in a commercial environment and to develop a time saving alternative methods for sealing quality analyses of PET bottles. (c) 2006 Elsevier Ltd. All rights reserved.