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Planning mold sampling locations

Mold Testing Sampling Plan

A sampling plan defines what you will test, where you will test, and how you will interpret results.

Define the Goal

Testing should answer a specific question such as documenting conditions, verifying remediation, or investigating symptoms without a visible source.

  • Document conditions for a dispute or claim
  • Verify remediation success
  • Compare multiple rooms for exposure clues
  • Confirm visible growth on materials

Build a Sampling Hypothesis

A good sampling plan starts with a theory: where moisture is coming from, how spores may be moving, and what results would confirm or rule out that theory.

  1. 1

    Identify suspected sources

    Leaks, condensation, or water damage locations are your starting point.

  2. 2

    Define exposure pathways

    Consider how air moves through rooms and HVAC returns.

  3. 3

    Decide what results would change the plan

    Sampling should drive a decision, not create uncertainty.

Select Sample Types

Air Sampling

Best for documenting overall indoor conditions. Requires an outdoor control sample.

Air sampling guide.

Surface Sampling

Confirms whether a stain or growth is mold and identifies the dominant type.

Surface sampling guide.

Dust Testing

Shows longer term patterns using settled dust. Useful for chronic concerns.

Dust testing guide.

Choose Locations

  • At least one outdoor control sample for air testing
  • Rooms with visible damage or musty odors
  • Rooms where symptoms are reported
  • A clean reference room for comparison

How Many Samples

  1. 1

    Start with a baseline

    One outdoor and one indoor sample establish context.

  2. 2

    Add suspect rooms

    Sample rooms with visible damage or odors.

  3. 3

    Add a reference room

    A clean area helps comparison across the home.

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3 more sampling guidelines

Avoid Sampling Errors

  • Do not test immediately after cleaning or disturbance
  • Keep windows closed before air sampling
  • Avoid sampling near open doors or vents
  • Use consistent timing for indoor and outdoor samples