Odors and vapors are particles that are diffused through the air. If something--such as a duct tape barrier--hinders the particles from diffusing, then the odors and vapors are contained.
Johnson & Johnson's Permacel Division created duct tape during World War II to keep moisture from getting into ammunition cases. Moisture diffuses through the air in a similar manner of the odors and vapors. Therefore, duct tape, if used as a barrier, can be used to contain odors and vapors as well.
Although some swear that duct tape can solve any problem, it can't contain all odors and vapors. One must consider the pressure intensity of the odors and vapors emitting from their source. Also, the amount of duct tape being used and the way it's applied to the material will affect duct tape's success on keeping the air ventilated successfully.