100+ Free InterNACHI Mold Inspector Practice Questions

The exam and the prerequisite courses ('How to Perform Mold Inspections' and 'Advanced Mold Inspection Training') are FREE for InterNACHI members. The cost of the credential is therefore included in InterNACHI membership dues (currently around $49 per month). There is no separate proctoring or testing-center fee — the final exam is delivered online through the InterNACHI School.

The InterNACHI mold inspector final exam contains 120 multiple-choice questions, many of which reference photographs or images. The exam uses weighted scoring: individual questions and individual answer choices carry different point values, and passing requires meeting an approximate 80-point weighted cut-off across the test. The exam is self-paced and delivered online.

The exam covers mold biology (common genera such as Stachybotrys, Aspergillus, Penicillium, and Cladosporium; mycotoxins; allergens), health effects on sensitive populations, moisture-intrusion sources (plumbing, roof, foundation, HVAC condensation, high humidity), non-invasive inspection methodology (visual, infrared, moisture meter, hygrometer), IAC2 sampling procedures (air, surface, bulk, outdoor controls), laboratory analysis (direct microscopy, culture, ERMI/HERTSMI-2), and writing reports per the IAC2 Standards of Practice.

The IAC2 Mold Inspection Standards of Practice require two outdoor air samples to serve as the control (or background) for indoor sample interpretation. The two samples should be collected on the windward and leeward sides of the building under clean, calm, above-freezing conditions, away from rain, and away from doors, vents, or overhangs. Outdoor samples establish the baseline mold profile naturally present in the air at the time of inspection.

The IAC2 Standards of Practice and InterNACHI's Code of Ethics strongly discourage the same person from performing both the mold inspection and the remediation on the same property due to the inherent conflict of interest. The inspector identifies, samples, and reports on apparent mold and conditions conducive to growth; the inspector recommends a qualified remediation contractor rather than performing remediation themselves. Some states (e.g., Florida, Texas, New York) prohibit this combination by law.

Non-viable air sampling (spore traps such as Air-O-Cell or Allergenco-D) captures all airborne mold spores — living and dead — on an adhesive surface for direct microscopic identification and counting. Non-viable is the most common method because results are fast and capture dead spores that still cause allergic reactions. Viable sampling (impactors such as Andersen N-6 onto agar plates) captures only living spores that grow into colonies for culturable identification and CFU/m3 counts. Viable sampling enables genus and species identification but underestimates total airborne mold.

Indoor relative humidity sustained above 60% — and especially above 70% — substantially increases the risk of mold growth on porous surfaces such as drywall, wood, and fabric. EPA, ASHRAE, and IAC2 generally recommend keeping indoor relative humidity between 30% and 50%, with 60% as the upper bound. Mold can also grow at lower bulk RH on cold surfaces where condensation forms (the relevant variable is surface RH, not just air RH). Mold inspectors document RH and temperature with a hygrometer at every inspection.