Authority · IICRC S520 Reference
Mold Conditions.
Cond 1, Cond 2, Cond 3 — Explained.
The IICRC S520 standard classifies mold situations into three conditions based on whether spores are airborne, settled, or actively growing. Condition determines the protocol, the containment, the materials that must be removed, and whether a clearance test is required. Misjudging condition is the most common reason mold returns within months— typically because the source of moisture wasn’t identified and stopped.
The Three Conditions
Condition 1
Normal Fungal EcologyWhat it means
Indoor spore profile matches outdoor reference at similar concentrations. No active growth. No remediation required. Goal state after successful work.
When seen
Healthy environments. Post-remediation clearance test result. Pre-purchase inspection negative results.
DRR Protocol
No action required. Document as baseline if a precautionary inspection was requested.
Condition 2
Settled SporesWhat it means
Visible mold residue from a prior event on surfaces. No active growth at inspection time. Spores can re-aerosolize when disturbed.
When seen
Aftermath of a contained event that wasn't fully cleaned. Storage areas with old water damage. Properties with prior unresolved mold.
DRR Protocol
HEPA cleaning of all surfaces, removal of contaminated porous materials (carpet pad, insulation, drywall paper if affected), antimicrobial treatment of remaining hard surfaces, post-remediation verification.
Condition 3
Active GrowthWhat it means
Visible mold colonies actively growing on surfaces. Always associated with an active or recent moisture source. Highest urgency.
When seen
Behind drywall after a water loss. HVAC return-air chambers with condensation. Crawlspaces and attics with vapor barrier failure. Around plumbing leaks.
DRR Protocol
Source-of-moisture identification and stoppage (Step 1, mandatory per S520). Full containment with negative-air HEPA filtration. Removal of contaminated porous materials. Antimicrobial treatment. Third-party clearance test confirming return to Condition 1.
Frequently Asked Questions
What is Condition 1 in mold remediation?
Condition 1 is normal fungal ecology — the indoor mold spore profile is consistent with the outdoor reference at similar concentrations and species mix. No active growth is present, no settled mold residue from a prior event remains, and no remediation is required. Condition 1 is the goal state after successful remediation, and the threshold a clearance test must demonstrate.
What is Condition 2 in mold remediation?
Condition 2 is settled spores — visible mold residue from a previous event remains on surfaces, but no active growth is present at the time of inspection. Settled spores can become aerosolized when disturbed (cleaning, demo, HVAC operation) and re-deposit elsewhere. IICRC S520 calls for HEPA cleaning and removal of contaminated porous materials, with post-remediation verification that the area returns to Condition 1.
What is Condition 3 in mold remediation?
Condition 3 is actual growth — visible mold colonies are actively growing on surfaces, often associated with a moisture source (leaking pipe, condensation, prior water loss). Condition 3 always requires source-of-moisture identification and stoppage, full IICRC S520 containment with negative-air HEPA filtration, removal of contaminated porous materials, antimicrobial treatment, and a post-remediation clearance test confirming return to Condition 1.
How is mold condition determined?
An IICRC S520-certified inspector determines the condition through visible inspection, surface sampling (tape lift or swab), air sampling (spore-trap cassettes processed by an accredited lab), and moisture mapping. The determination is documented at the start of every job. DRR is IICRC S520-certified and uses third-party labs for sample analysis to ensure independent results.
Why does the EPA's 10-square-foot guideline exist, and is it safe to follow?
The EPA's homeowner-cleanup guideline of 10 square feet or less assumes (1) you have already identified and stopped the source of moisture, (2) the affected materials are non-porous or easily replaced, and (3) no occupants have mold-related health sensitivities. In Phoenix conditions — slab-on-grade construction, HVAC supply runs through walls, swamp coolers — the moisture source is typically hidden behind drywall, which means homeowner cleanup addresses the visible part while the moisture source continues to grow new colonies. Even at small visible scale, an inspection is the safer first step.
What is a clearance test, and why does it matter?
A clearance test is a post-remediation evaluation that confirms the affected area has returned to Condition 1 (normal fungal ecology). It includes visible inspection, surface sampling, and air sampling that's compared against an outdoor baseline. Independent third-party clearance testing is required for healthcare environments, often for commercial environments per insurance policy, and is best practice for residential. DRR coordinates third-party clearance on every Condition 3 remediation.
Why does mold come back after remediation sometimes?
Mold returns when the source of moisture isn't identified and stopped. IICRC S520 explicitly requires source identification as a prerequisite for remediation — treating the visible growth without addressing the leak, condensation, or vapor barrier failure that's feeding it produces a cosmetic result that fails within months. Every DRR mold remediation begins with moisture-source identification, and the source fix is documented as Step 1 of the project.
Suspect mold? Call us before you touch it.
IICRC S520-certified inspection identifies the condition, locates the moisture source, and produces a remediation scope your insurance carrier accepts. Disturbing visible growth before containment is set up will distribute spores throughout your building.
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