Abstract: An apparatus and method for testing the integrity of a filter under humid conditions is provided. The apparatus includes an injection assembly which is located on a first side of the filter and a detection assembly which is spaced from the injection assembly and located on a second side of the filter. The injection assembly injects a mixture of an air stream and a hydrophilic test chemical vapor of a known concentration through the filter. The injection assembly includes a sealed vaporizer which generates the mixture of the air stream and the hydrophilic test chemical vapor. The vaporizer includes a contact bed having an inert packing media for vaporizing the hydrophilic test chemical. The detection assembly detects a concentration peak of the hydrophilic test chemical vapor exiting the filter. The detection assembly includes a chemical sampling member, a chemical enriching member and a chemical detector.