What Is IICRC S520?

The IICRC S520 Standard for Professional Mold Remediation is the primary industry reference document governing how professional mold remediation should be conducted in North America. Published by the Institute of Inspection, Cleaning and Restoration Certification, it establishes minimum guidelines for assessment, planning, containment, source removal, cleaning, and post-remediation verification.

The standard defines remediation levels based on affected area size and material type. Level 1 (small isolated areas under 10 sq ft) requires minimal containment and can be performed by trained building maintenance staff. Level 2 (10–100 sq ft) requires more protective measures and containment. Level 3 (over 100 sq ft) requires full containment, negative pressure, HEPA equipment, and worker decontamination. These levels guide what level of professional is needed and what procedures must be followed.

For homeowners, the S520 matters because it establishes what a competent contractor should do. A remediation company that does not follow S520 protocols — for example, skipping containment, failing to use HEPA equipment, or not performing post-remediation verification — is not performing work to industry standard. You can ask contractors whether they are IICRC-certified and whether their work plan follows S520.

The standard is also the reference document used in insurance claims. When a homeowner files a mold claim, the adjuster and contractor typically reference S520 to determine appropriate scope of work and costs. Understanding its basic framework helps homeowners have more informed conversations with both contractors and insurance representatives.