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IICRC S500 and S520: the standards behind water and mold work

Published: 1,138 words5 min read

A restoration company's website that mentions "S500" or "S520" is pointing at two documents published by the IICRC (the Institute of Inspection, Cleaning and Restoration Certification). Here is what they are, what they say about contaminated water, and how to check a company's IICRC claims.

What S500 and S520 are

ANSI/IICRC S500 is the Standard for Professional Water Damage Restoration. According to the IICRC, it describes the procedures to follow and the precautions to take when restoring water damage in residential, commercial and institutional buildings, along with their systems and contents. Its listed components run from psychrometry and drying technology to HVAC restoration, contents, documentation and large-loss projects. When we checked iicrc.org in September 2026, the current edition was the fifth, published in 2021, and a new consensus body had begun revising it.

ANSI/IICRC S520 is the Standard for Professional Mold Remediation. The IICRC calls it a procedural standard for remediating mold-damaged structures and contents. Its components include remediator qualifications, structural and HVAC remediation, contents, and post-remediation verification. The fourth edition, from 2024, was current when we checked.

The two connect. S500 tells a water restorer who finds or suspects mold to refer to the current S520.

Who writes them

The IICRC is a non-profit certification body for the inspection, cleaning and restoration trades. Its standards are written by consensus bodies of volunteers and approved by the American National Standards Institute, which is where the "ANSI" prefix comes from. The IICRC describes them as voluntary consensus standards that restorers accept as the standard of care.

Two practical points follow. The standards are sold, not published free, through the IICRC's webstore. And the IICRC says it does not answer technical questions about applying them; it points people to a Certified Firm or to buying the standard. So a homeowner will rarely read S500 itself. What you can do is ask a company how its work lines up with it.

What "Category 3" water means

S500 sorts water by how contaminated it is, and the category a restorer assigns drives the scope of work. The IICRC has published the S500 definition of the most serious category. Category 3 water "is grossly contaminated and can contain pathogenic, toxigenic, or other harmful agents and can cause significant adverse reactions to humans if contacted or consumed." The examples it gives include sewage, wasteline backflows from beyond a trap whatever the water looks like, seawater flooding and rising water from rivers or streams.

S500 has the restorer set the category through a preliminary determination made after inspecting the site. For Category 1 water, the restorer can proceed without contamination controls. For Category 2 or 3, remediation should come before restorative drying, with contamination controls and worker protection.

In a position statement dated February 2026, the S500 consensus body added that wind-driven rain and other weather-related water are not automatically Category 3. The test is whether the water is grossly contaminated, whatever route it took into the building.

S500 also defines classes of water damage. We haven't described them here because we couldn't confirm the wording on a free IICRC page.

A certified technician is not a Certified Firm

Websites often blur the two.

An IICRC certification belongs to a person. A technician earns it by passing IICRC certification exams, which the IICRC offers across inspection, cleaning and restoration specialties.

An IICRC Certified Firm is a business. The IICRC defines it as a company that employs one or more IICRC Certified Technicians. To apply, a firm needs at least one active certified technician and proof of general liability insurance. Firms renew each year and sign the IICRC Code of Ethics. A company can employ a certified technician and still not be a Certified Firm.

The IICRC also keeps a public list of invalid firms. These are companies it says used the Certified Firm logo without being registered, which its logo policy doesn't allow.

How to check a company yourself

Start with the IICRC Global Locator on iicrc.org. The IICRC says it connects homeowners and business owners with certified firms and technicians. Search the company's name and check that the firm itself appears, since a listed technician is a different credential. You can also contact the IICRC with the company name and ask it to confirm the credential.

Then read the invalid firms list. If a company you're considering is on it, ask about it directly. And if a website shows the IICRC logo but the firm isn't in the locator, the IICRC has a route to report it.

Questions to ask the company

  • Is the company itself an IICRC Certified Firm, or are you referring to a technician's certification?
  • Which technician on my job holds which certification?
  • What category did you assign this water, and what did you see that decided it?
  • If you find mold, will you follow S520, and who checks the work when it's finished?
  • Will I get your moisture readings and photos in writing?

How Restoration Index counts this

The Evidence Score treats the two kinds of claim differently. A company naming S500 or S520 on its own site counts as a self-reported transparency item, worth 4 points. An IICRC Certified Firm record is a third-party qualification worth 8 points, and only a check against the IICRC's own records earns it. We haven't logged that check for any company yet, so every profile shows it as not verified. See how the Evidence Score works for the full weights.

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