IICRC S520

What it means

The S520 is the IICRC’s mold remediation standard, accredited by ANSI. The IICRC lists the 4th edition (2024) as current, with earlier editions from 2003, 2008 and 2015. The IICRC describes it as a procedural standard for remediating mold-damaged structures and contents in homes, commercial and institutional buildings.

Its sections include principles of mold remediation, antimicrobial chemicals and coatings, remediator qualifications, safety and health, documentation, inspection, structural, HVAC and contents remediation, and post-remediation verification. It also defines the role of the indoor environmental professional who assesses a building.

Why it matters to your home and your bill

A written plan based on the S520 gives you something to hold a contractor to. In states without mold licensing, which is most of the country, asking for a written S520-based protocol is one of the best protections you have. EPA’s homeowner guidance also tells you to ask contractors to follow EPA or IICRC guidelines. If a quote says “per S520,” ask which steps that covers: containment, removal, cleaning, drying and who does verification. Our mold remediation process page walks through those steps in plain terms.