Inspection and Sampling Methodology
Inspection and sampling methodology
This domain tests the inspection sequence, sampling decision logic, and field technique that a defensible report depends on.
Inspect first, sample second
Sampling never substitutes for a visual and moisture assessment. Build a hypothesis - for example, growth behind a shower surround from failed caulk - and choose methods that test it. IAC2 practice and most laboratory guidelines endorse sampling only to confirm suspected concealed growth, document a complaint, or verify remediation.
Field sequence and tools
Start outside: grade, downspouts, roof covering, flashings, vents. Move to the attic (baffles, sheathing staining, exhaust termination), then the living space (under sinks, behind appliances, window frames, HVAC closet), then basement or crawlspace. Measure with a pin or pinless moisture meter, a thermo-hygrometer and an infrared camera; use a borescope inside cavities.
Sample types
- Air, non-viable (spore trap): Air-O-Cell or Allergenco cassette, typically 75–100 L at 15 L/min for five minutes, with the pump calibrated before and after. Genus-level counts, no viability.
- Air, viable (culture): Andersen impactor; species-level but biased toward fast growers.
- Surface: tape lift for morphology; swab for culture or PCR; bulk for materials.
- Dust PCR / ERMI: species-specific DNA from dust; a screening tool.
Sampling design
Run at least one outdoor control plus one indoor sample per distinct zone, more where multiple HVAC zones or floors exist. Take the outdoor control the same day, ideally before indoor sampling. Maintain closed-building conditions, generally 6–12 hours; avoid sampling during rain, right after vacuuming, or with the HVAC fan cycling if documenting settled conditions. Use unique sample IDs, a documented chain of custody and an accredited laboratory.
Worked example
A client requests air samples after seeing dark material behind a bedroom dresser. Sample an outdoor control, the bedroom and a reference room; add a tape lift of the visible growth. The tape lift identifies the organism directly; the air data show whether the room is elevated relative to outdoors.
Traps
Sampling with no hypothesis or outdoor control; using settle plates; taking one sample and calling it proof of hidden mold.