49 CFR § 178.604 - Leakproofness test.
(2) This test is not required for inner packagings of combination packagings.
(b) Number of packagings to be tested -
(i) Before they are first used in transportation; and
(ii) Prior to reuse, when authorized for reuse by § 173.28 of this subchapter.
(2) Design qualification and periodic testing. Three samples of each different packaging must be tested and must pass the leakproofness test. Exceptions for the number of samples used in conducting the leakproofness test are subject to the approval of the Associate Administrator.
(c) Special preparation - (1) For design qualification and periodic testing, packagings must be tested with closures in place. For production testing, packagings need not have their closures in place. Removable heads need not be installed during production testing.
(d) Test method. The packaging must be restrained under water while an internal air pressure is applied; the method of restraint must not affect the results of the test. The test must be conducted, for other than production testing, for a minimum time of five minutes. Other methods, at least equally effective, may be used in accordance with appendix B of this part.
(e) Pressure applied. An internal air pressure (gauge) must be applied to the packaging as indicated for the following packing groups:
(1) Packing Group I: Not less than 30 kPa (4 psi).
(2) Packing Group II: Not less than 20 kPa (3 psi).
(3) Packing Group III: Not less than 20 kPa (3 psi).