Most mold remediation contractors have had a call that they dread. During the course of a project where part of the home or commercial building has been isolated, an occupant complains that they can smell the mold and have become ill because of "leaks" from the containment. An emergency return trip to the site, a visual review of all containment barriers, and confirmation of adequate and consistent negative pressure in the work zone all attest to the fact that the mold remediation project has not led to any cross-contamination. Despite all this, the occupant insists that they can "sense" the contamination in areas of the building where it was not present prior to the start of work.

In many cases, the situation just devolves into a "he said, she said" argument where each side is convinced that they are correct. Even trying to address the issue with data, such as spore trap air samples, can be tricky because the samples represent a spot time after the potential cross-contamination has occurred. Surface tape samples might be useful, but unless similar pre-work samples were collected from the area in question, it would still be difficult to determine whether any recovered fungal contamination was there before the work started or a result of some problem with the project.