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Mold Removal and Remediation: What it Means to Follow ANSI/IICRC S520 Standards to Achieve Source Removal

Post 2 of 3 in our Mold Remediation Series

Mold remediation has been a controversial topic since it was recognized as a service provided by many remediation contractors.

The steps of successful mold remediation include correcting the source of moisture, the proper use of containment, partial pressure differentials, HEPA filtration, and the proper use of personal protective equipment (PPE).

The use of chemicals in the cleaning and restoration industry has also been controversial. I have been called the “anti-chemical queen” for years. Although I am not opposed to chemical use, my biggest concerns are that most contractors do not know the products that they are using, that they are not using them according to the manufacturer’s directions, and that salespeople often promote their products by making false claims about what their products can and cannot do. The biggest false claim made is about using chemicals to kill mold.

What are the proper IIRC standards for cleaning mold? What is the role that chemicals should play during a remediation job? I have served on the committee that writes and establishes guidelines and updates for the standard of care for mold remediation (the S520), and I will break down the answers to these questions below. 

Moldy Ceiling

What is the Goal of Mold Remediation?

The fundamental principle of mold remediation is cleaning with source removal as the intended target of the job. This means that you should use a product that contains a surfactant or detergent that will allow for the contamination to be suspended and physical removal to be achieved.

Most products used in mold remediation are typically hypochlorite or hydrogen peroxide-based products. They are intended to be used last after cleaning has been done in order to lift or remove the stain that dematiaceous (dark pigmented) molds leave behind. In many cases, sampling after cleaning will show acceptable results, but the dark staining that is left behind creates concerns for building owners and for many hygienists. These products are commonly used for aesthetics.

Using chemicals to kill mold should not be the goal of the remediation contractor.

Non-viable mold spores contain the same toxigenic and/or allergenic properties as their viable counterparts. The majority of mold is non-viable to begin with. This can be easily demonstrated when comparing a culture plate to a spore trap in which only the viable mold spores will be able to grow on the media in the plate. The mold can be as much as 75% less than what is identified on a spore trap.

How to Safely and Effectively Use Chemicals If Your Mold Job Requires Them

Bacteria and viruses that are routinely present in Category 3 water damage, crime, and trauma are easily killed when chemical products are applied correctly. This is a beneficial step in remediating these types of projects because if there is sufficient kill of these organisms they cannot invade the human body and cause disease or illness.

For any remediation job that requires the use of chemicals, the safety of the technicians applying these products and the residual effects that could potentially impact the occupants of the building MUST be considered. Not only can some of the products available to the restorers damage certain materials and surfaces, but they are extremely hazardous to the end-user, the technician.

The appropriate personal protective equipment such as a full-face cover is a MUST, as well as being familiar with the safety data sheet, and reading the ENTIRE label prior to the purchase and use of the product. Remediation contractors using chemical products MUST be trained to understand the product and the effect that it will have within the structure. The indiscriminate application of chemicals is not acceptable and may result in liability to the restorer.


half face respirator

Chemical use should never be done to take the place of source removal. All chemicals have limitations. There is no silver bullet that replaces the fundamental practice of cleaning, using containment, and working under partial pressure differentials.

Products that are applied with a wet fogging machine into buildings have several limitations. For chemical products to be effective, they have to be used at the concentration stated by the manufacturer. In addition, they must make adequate contact with the surface that they are applied to and must remain in full contact for the necessary time (known as the dwell time). The efficacy of any fog, gas, or vapor-phase antimicrobial application is compromised when sufficient concentration cannot be maintained in a space for the necessary time.

It is also important to note that all chemicals are tested for their efficacy on pre-cleaned, non-porous surfaces and under ideal conditions created in a testing environment. This is not how the products are being used in the field. Real-life performance is generally less than the efficacy claims stated by the product label.

For example, if you are applying Fiberlock IAQ Advanced Peroxide Cleaner or Bioesque Botanical Disinfectant to remove mold stains left behind you can find detailed instructions about proper application underneath the tab "related documents". The dwell time is listed as ten minutes.

Following the Correct Standard for Mold Remediation

The ANSI/IICRC S520 Standard For Professional Mold Remediation and the IICRC R520 Reference Guide For Professional Mold Remediation defines the fundamental principle of mold remediation as source removal.

In some instances, cleaning the surface with a detergent and minimal water may do the trick. In other instances, it may require the removal of the materials supporting the fungal growth, either because it cannot be effectively cleaned or the material has deteriorated in structural integrity due to water damage and/or mold growth.

The statement that the S520 promotes the removal of materials is inaccurate. That decision is left to the remediation contractor based on whether or not the material can be cleaned. For example, drywall is considered porous and is generally removed and disposed of. Wood framing is considered semi-porous and is often cleaned using a combination of damp wiping, HEPA vacuuming, and an abrasive step such as wire brushing, hand sanding, or media blasting.

Moldy Apartment


Most guidance documents written with recommendations for mold remediation used specific amounts of visible mold to dictate the remediation activities. The S520 and R520 manuals made a philosophical shift away from using the metric of visible square feet of mold growth and instead use defined conditions of mold contamination.

Condition 1 is the ultimate goal of the contractor: to return the building back to a normal fungal ecology that is comparable to an outside reference sample or an unaffected part of the building.

The main reason the standard uses conditions is that a contractor might think that a job was completed due to there being only a small amount of visible mold growth while missing the hidden mold growth in wall cavities, flooring assemblies, and substructures. This also allows for the contractor to use third-party testing to identify Condition 2 in a building where the settled spores still require removal.

Condition 3 refers to areas that have visible mold growth present.


While there are many ways to approach a mold remediation project, the contractor should follow the standard of care as outlined in the ANSI/IICRC S520. It is critical to complete specialized training (like IICRC classes) so that you understand the mechanics of containment, airflow management, and learn how to properly use a negative air machine to reduce your liability. The IICRC standards are developed by volunteers that have actually been involved in the industry in many different facets and define the practices that are common to reasonably prudent members of the trade who are recognized in the industry as qualified and competent.

Enjoyed reading this post? Read the following articles:


Mold Blog Post 3 Cover-1

Where do Mold Hazards Lurk_

Asbestos containment area


Take your education beyond our blogs:

Aramsco/ Interlink Supply Training Schedule (

IIRC Applied Microbial Remediation Tech


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