Between the years of 2010 – 2018, I was a part of a research project that looked to answer that question. The parameters of each project required that a thorough pre-remediation assessment was performed, that included, among other things, surface and air samples; they required that surface and air samples were collected during any post-remediation assessment; they required an independent, accredited laboratory – with no knowledge of the research project – perform all laboratory analysis; they required that the same mold assessor be involved in all assessments of the project; and they prevented the mold assessor from operating as project manager. The projects were performed by different mold remediators. Some remediators would clean surfaces with HEPA vacuums and wiping of surfaces; processes and products (if any) varied. Some remediators did very little, next to spraying surfaces after demolition. Still other remediators were in-between, perhaps using a broom to sweep floors before spraying a biocide onto surfaces. All of the latter two types of mold remediators utilized some combination of chemical biocides, spraying and/or fogging surfaces and/or the air in the work area.

Well, those mold remediators who took the time to meticulously clean surfaces in the work area had a 100% post-remediation success rate, meaning all surface and air samples demonstrated a normal mold population in the work area. The latter two types of mold remediators (those with little to no surface cleaning in the work area) did not fair so well. As it pertained to air samples, results were mixed: 74% of air samples showing a normal airborne mold spore population. As it pertained to surface samples: 91% of surface samples showed an abnormal surface mold spore population. When the latter group was provided guidance on how to complete the job and surfaces were meticulously cleaned, the success rate of the post-remediation sampling rose to 100%. (That said, not all mold remediators would accept guidance. Those that did not continued to fail surface sampling in subsequent post-remediation assessments.)