What Is IICRC S520?
The IICRC S520 Standard for Professional Mold Remediation is the primary industry standard for mold assessment and remediation in the United States. Developed by the Institute of Inspection, Cleaning and Restoration Certification (IICRC), it provides procedures for addressing mold contamination in buildings.
First published in 2003 and regularly updated (current version: 2021), S520 represents the consensus of industry professionals, scientists, and health officials on best practices for mold remediation.
Industry Standard, Not Law: While not legally enforceable in most jurisdictions (including Oklahoma), IICRC S520 is widely adopted and often referenced in contracts, insurance requirements, and legal proceedings. Professional remediators typically claim to follow this standard.
Key Principles
1. Moisture Source First
Identify and address the water source before beginning remediation. Remediation without moisture correction is futile — mold will return. This is the most commonly violated principle.
2. Containment
Isolate work areas to prevent cross-contamination. Uses polyethylene sheeting, negative air pressure, and HEPA-filtered air scrubbers. Size and complexity depends on affected area and building layout.
3. Source Removal
Remove and dispose of contaminated porous materials that cannot be effectively cleaned — moldy drywall, carpet padding, insulation. You cannot reliably clean mold out of porous materials.
4. Cleaning & Treatment
Clean salvageable materials using appropriate methods: HEPA vacuuming, damp wiping with appropriate solutions, antimicrobial treatment where appropriate. Methods vary by material type.
5. Post-Remediation Verification
Independent inspection and/or testing to confirm successful remediation before reconstruction. S520 explicitly recommends third-party verification, not self-assessment by the remediator.
Condition Categories
S520 classifies indoor environments into three conditions that guide remediation approach:
| Condition | Description | Action |
|---|---|---|
| Condition 1 | Normal fungal ecology (background levels typical for location) | No remediation needed |
| Condition 2 | Settled spores but no active growth (contaminated but dry) | Cleaning may be sufficient |
| Condition 3 | Active mold growth present (contaminated and wet) | Full remediation required |
The S520 Remediation Process
- Assessment — Identify extent of contamination and moisture source
- Remediation Planning — Written scope of work with specific procedures
- Containment Setup — Isolate work area from occupied spaces
- Source Removal — Remove contaminated porous materials
- Structural Cleaning — Clean remaining surfaces and framing
- HEPA Vacuuming — Capture settled spores from all surfaces
- Verification — Third-party inspection and/or testing
- Reconstruction — Replace removed materials (typically separate contractor)
What This Means for Homeowners
- Ask about S520 — Reputable remediators follow this standard and should be able to explain their process
- Request a written scope — Should reference containment, removal, cleaning, and verification
- Independent testing — Post-remediation verification by third party, not the remediator
- Don’t skip moisture repair — Remediation without source fix = recurring problem and wasted money
- Get clearance before reconstruction — Don’t close walls until verified
TrueSight’s Role: We provide independent pre-remediation assessment and post-remediation verification testing. As inspectors only (not remediators), we have no conflict of interest in findings. Learn more →
Oklahoma Context
No State Licensing
Oklahoma does not require mold remediators to be licensed. This makes S520 compliance even more important as a quality indicator. Ask prospective remediators if they follow S520 and can provide documentation.
Insurance References
Oklahoma insurance companies often reference S520 when evaluating mold claims. Remediation that deviates from the standard may face coverage questions. Documentation of S520-compliant work strengthens claims.
Legal Disputes
In Oklahoma mold-related lawsuits, S520 is often cited as the standard of care. Remediators who deviate significantly may face liability. Homeowners should keep documentation of adherence to this standard.
Resources & Citations
- IICRC.org — Purchase the full S520 standard
- IICRC S500: Standard for Professional Water Damage Restoration (companion document)
- IICRC R520: Reference Guide for Professional Mold Remediation
- EPA. “Mold Remediation in Schools and Commercial Buildings.”