A bulk sample is an actual piece of suspect building material, a cut of drywall, a tuft of carpet, a chunk of insulation, removed and sent to a lab to confirm whether mold is growing on it and which genus it is.
What is a bulk sample?
A bulk sample is one of three common surface methods, alongside the swab sample and the tape lift. Where a tape lift captures only the surface layer, a bulk sample brings the whole material so the lab can examine growth through it, which is useful when contamination may be inside the substrate, not just on its face. It is destructive by nature, so it suits material already being removed or sacrificed. The lab reports presence and genus, typically semi-quantitatively (rare, occasional, abundant), not a concentration, because there is no air volume involved (AIHA, Green Book).
Why it matters to a mold inspection
A bulk sample confirms a source that air sampling only hints at. When a spore trap shows a normal air count but a wall reads wet and stained, a bulk cut can prove growth that never aerosolized, which is exactly the Stachybotrys failure mode. The EPA stresses that visible mold does not require sampling to justify removal, so a bulk sample is a documentation and identification tool, not a prerequisite for remediation (EPA, Mold Remediation in Schools and Commercial Buildings). See bulk, swab, and tape-lift sampling and air vs surface sampling.
MoldMind records the substrate, collection method, and the semi-quantitative result for each bulk sample, so a destructive sample is tied to the exact material and location it came from.
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Sources
- AIHA, Green Book: surface methods report semi-quantitatively, not as air concentrations.
- EPA, Mold Remediation in Schools and Commercial Buildings: visible mold does not require sampling before removal.