InterNACHI Mold Inspector cheat sheet

Mold requires four conditions to grow: moisture (water activity ≥0.80), organic food source (cellulose, dust, skin cells), suitable temperature (typically 5–40°C, optimal 20–30°C), and oxygen (molds are obligate aerobes).

Water activity (aw) measures available water; xerophilic molds grow at aw 0.75–0.85, mesophilic at 0.85–0.90, hydrophilic at >0.90. Most building molds require aw ≥0.80.

Fungi are classified as Ascomycota (e.g., Aspergillus, Penicillium), Basidiomycota (e.g., wood-decay fungi), and Zygomycota (e.g., Rhizopus). Stachybotrys chartarum is a slow-growing, cellulose-loving mold requiring high moisture (aw >0.90).

Mold reproduces via spores (conidia or sporangiospores); spore germination requires moisture and nutrients. Spores are ubiquitous outdoors (10^3–10^4 spores/m³) and indoors; elevated indoor levels indicate amplification.

Growth curve: lag phase (spore germination), exponential phase (mycelial growth), stationary phase (sporulation). Visible growth typically appears in 24–72 hours under optimal conditions; some species require 7–14 days.

Molds produce mycotoxins (e.g., trichothecenes from Stachybotrys, aflatoxins from Aspergillus flavus), MVOCs (microbial volatile organic compounds) causing odors, and allergens (proteins in spores and hyphae).

Indicator organisms: Cladosporium and Alternaria are common outdoor molds; Aspergillus and Penicillium often indicate indoor moisture; Stachybotrys requires chronic water damage (cellulose, high moisture).

Temperature range: psychrophilic (<10°C), mesophilic (10–40°C), thermophilic (>40°C). Most indoor molds are mesophilic; refrigeration does not stop mold growth, only slows it.

pH range: molds tolerate pH 2–11, optimal 4–6. Acidic surfaces (e.g., gypsum board) can support mold if moisture is present.

Moisture sources: roof leaks, plumbing leaks, window/door leaks, foundation cracks, rising damp, condensation, high indoor humidity, flooding, and construction moisture.

Building envelope components: roof, walls, windows, doors, foundation, and vapor barriers. Failure of any component allows water intrusion; inspect flashings, sealants, and drainage.

Condensation occurs when warm, moist air contacts a surface below the dew point. Thermal bridges (e.g., metal studs, uninsulated corners) create cold spots and condensation.

Relative humidity (RH) above 60% indoors can support mold growth; maintain indoor RH between 30–50% (ASHRAE recommends ≤60% in summer). Use psychrometric chart to relate RH, temperature, and dew point.

Water intrusion categories: Category 1 (clean water), Category 2 (grey water), Category 3 (black water). Category 3 water requires removal and disinfection; mold can develop within 24–48 hours.

Infrared thermography and moisture meters (pin-type and pinless) are non-invasive tools to detect hidden moisture; confirm with invasive methods (e.g., moisture readings, borescope).

Roof leaks often originate at penetrations (vents, chimneys), valleys, and flashing; check attic insulation for stains and rafters for water marks.

Basement moisture: hydrostatic pressure, failing drain tile, and poor grading. Check for efflorescence (white mineral deposits) indicating water movement through masonry.

HVAC systems: condensate pan overflow, clogged drain lines, and high humidity in ductwork can cause mold amplification; inspect air handlers and ducts for visible growth.

Health effects of mold exposure: allergic rhinitis, asthma exacerbation, hypersensitivity pneumonitis, and opportunistic infections in immunocompromised individuals.

Mycotoxins (e.g., trichothecenes, aflatoxins) are not volatile; exposure occurs via ingestion, dermal contact, or inhalation of toxin-laden spores. Evidence of clinical effects from inhalation in buildings is limited but debated.

MVOCs (microbial volatile organic compounds) cause musty odors and can irritate eyes, nose, and throat; they are not reliable indicators of mold presence.

Risk groups: children, elderly, pregnant women, immunocompromised persons, and individuals with pre-existing respiratory conditions.

No established dose-response relationship for mold exposure; no regulatory standards for airborne mold concentrations. Interpret results with caution and avoid attributing specific illnesses to mold without medical evaluation.

Occupant interview: gather history of water damage, visible mold, odors, and health symptoms (timing, location). Document complaints and concerns.

Mold inspectors are not physicians; do not provide medical advice or diagnose. Recommend consulting a healthcare provider for health concerns.

Psychological effects: anxiety and stress from visible mold and odors can be significant; address occupant concerns with clear communication and remediation plan.

Legal and ethical: inspectors should follow standards of practice (e.g., InterNACHI) and avoid conflict of interest (e.g., performing remediation on inspected property).

Inspection protocol: exterior (grading, drainage, roof, walls), interior (visible mold, water stains, musty odors), HVAC, attic, crawlspace, and basement. Use moisture meter, hygrometer, and infrared camera.

Sampling methods: air sampling (spore trap, culturable), surface sampling (tape lift, swab, bulk), and dust sampling. Each method has limitations; combine with visual inspection.

Air sampling: use calibrated pump (e.g., 15 L/min for 5–10 min) with spore trap (e.g., Allergenco-D, Air-O-Cell). Collect outdoor control sample for comparison. Report results as spores/m³.

Surface sampling: tape lift for visible mold (identifies genus), swab for porous surfaces, bulk sampling for building materials. Document location and area.

Sampling strategy: sample suspected mold, control area (unaffected), and outdoor air. Avoid sampling after remediation without pre-remediation baseline.

Chain of custody: label samples with unique ID, location, date, time, and collector; maintain refrigeration for culturable samples; ship promptly to accredited lab.

Safety: wear PPE (N95 respirator, gloves, eye protection) when disturbing mold; contain area to prevent cross-contamination.

Documentation: photographs, moisture readings, floor plans, and written report. Note limitations (e.g., inaccessible areas, no destructive testing).

Sampling frequency: at least one outdoor control and one indoor sample per affected area; multiple samples for large areas. Avoid over-sampling; use professional judgment.

Laboratory methods: direct microscopy (spore trap, tape lift) identifies spores to genus; culture (viable) identifies species and provides CFU counts; PCR (DNA-based) identifies species but does not indicate viability.

Spore trap analysis: reports spore types and concentrations (spores/m³). Results are semi-quantitative; debris and hyphae fragments may be missed.

Culture analysis: reports colony-forming units (CFU) per sample; identifies viable molds. Results depend on media and incubation conditions; slow-growing molds may be overgrown.

Interpretation: compare indoor to outdoor concentrations. Indoor levels significantly higher than outdoor (e.g., >2x) suggest indoor amplification. Presence of water-damage indicator molds (e.g., Stachybotrys, Chaetomium) indoors is significant regardless of concentration.

Limitations: no standardized threshold for mold; results vary by sampling method and lab. False negatives possible if spores not captured or non-viable. Always interpret with visual inspection.

Laboratory accreditation: use labs accredited by AIHA-LAP, EMLAP, or NVLAP for mold analysis. Request lab report with method, detection limits, and analyst qualifications.

Report contents: sample ID, location, method, results (spore types, concentrations), interpretation, and recommendations. Avoid definitive health claims.

Quality assurance: duplicate samples, field blanks, and outdoor controls. Calibrate pumps before and after sampling.

Common genera: Aspergillus/Penicillium (indistinguishable under microscopy), Cladosporium, Alternaria, Stachybotrys (requires moisture), Chaetomium, Ulocladium, Epicoccum.

Remediation standards: follow IICRC S520 (Mold Remediation) and New York City Department of Health (NYCDOH) guidelines. Containment, PPE, and HEPA filtration required.

Remediation verification: post-remediation inspection and sampling (air and surface) to confirm mold removal. Visual inspection must show no visible mold or moisture.

Clearance criteria: no visible mold, moisture levels normal (<15% wood moisture), and indoor spore concentrations comparable to outdoor or control areas. Indicator molds (Stachybotrys) should be absent or at low levels.

Post-remediation sampling: air samples (spore trap) and surface samples (tape lift) from remediated areas and control areas. Use same methods as pre-remediation for comparison.

Reporting: include scope of work, remediation methods, verification results, and conclusions. State limitations and recommendations for further action.

Documentation: before/after photos, moisture readings, lab reports, and remediation contractor's report. Keep records for at least 5 years.

Occupant re-occupancy: only after clearance criteria met and remediation area dried. Advise occupants to maintain indoor RH <60% and address any moisture issues.

Conflict of interest: inspector should not be the remediator. Independent verification ensures objectivity.

Standards of practice: InterNACHI Mold Inspector SOP requires visual inspection, moisture assessment, and sampling (if requested). Report must be in writing and include limitations.