SURFACE AND WALL CAVITY SAMPLING

Surface Sampling

Surface samples are taken by tape lift for laboratory analysis to determine the types and concentrations of mold spores in a small, usually horizontal, surface area. Tape lift surface samples are always recommended in cases where there is visible black mold growth. Stachybotrys, a known toxic mold, often shows up in surface samples and not in air samples taken in the same area. This black mold may not release as many spores when wet. It is important to know if this type of mold is present.

While surface sampling will determine what types of mold are on a surface, they may not give a direct indication of what may be in the air. Surface sample spore counts are not quantified, their concentrations noted only as rare, moderate, heavy, etc. Also with surface sampling, no comparison is made with outdoor levels, unlike standard air sampling procedures. Many times, a combination of air and surface sampling provides the best overall indication of the presence and/or severity of a mold problem.

Wall Cavity Sampling

A large percentage of mold growth is often found on the inside of drywall in wall cavities hidden from view. Newer homes have become much closer to being “air-tight”, and mold in wall cavities may not show up in air samples taken in close proximity to the wall. Wall cavity samples can be taken similarly to indoor air samples, but with an extension to pull the air from within the wall cavity. The results below show a staggeringly high count of Aspergillus/Penicillium in a wall cavity, with much lower spore counts detected in the master bedroom closet on the other side of the wall.

No traces of Stachybotrys were detected in an air sample taken in the bathroom in the photo below. Though no sampling was performed after remediation was begun, it is likely that much of the mold found behind the shower walls was the toxic black mold Stachybotrys. Mold feeds more easily on the paper backing of drywall than on the painted or tiled side. Wall cavity samples are likely to have higher spore counts than air samples taken in the living areas and can help detect dangerous hidden mold sources.