Anthony Denatala, CMRS · August 7, 2026 · 8 min read
A research paper published in August 2025 in the Medical Research Archives uses language I have been using in client conversations for two decades: the water-damaged building is not just a building with a problem. It is a broken biological ecosystem. The paper, authored by four experienced indoor environmental professionals — Michael Schrantz, John Banta, Larry Schwartz, and David Lark — lays out the science behind what many of us in this industry observe every day in the field. I want to walk through what it says and what it means practically for a homeowner trying to understand what is happening in their property.
The paper opens with a history most homeowners have never heard. In 1993, the first U.S. government guidance on indoor mold set an action threshold of one square foot of visible Stachybotrys growth. By 2000, that threshold had been raised to ten square feet — and expanded to include all mold species. The EPA's 2001 publication reinforced best practices for containment and cleaning, but still depended on visible mold area to drive decisions.
The problem with a visibility-based standard should be obvious: most of the mold that causes health problems in a water-damaged building is not visible. It is behind drywall, inside wall cavities, in attic insulation, under flooring, inside HVAC components, and distributed through the building as microscopic spores and fragments that have been airborne and settled for months or years. You cannot see any of that. A home can look perfectly clean and still be heavily contaminated at the biological level.
The IICRC S520 standard, first published in 2003, was a meaningful step forward because it moved away from visible mold area entirely and introduced a three-condition classification system still used today. Condition 1 is normal fungal ecology — what a clean, dry building looks like. Condition 2 is residual contamination from a known Condition 3 source — spores and fragments distributed from active growth. Condition 3 is active mold growth, visible or hidden. The goal of remediation under S520 is to restore a Condition 2 or 3 building to Condition 1 baseline. The paper correctly notes that achieving that goal requires addressing both visible growth and the secondary subvisible contamination — and that most standard remediation scopes stop short of fully completing that second step.
Key finding from the research
"Mold spores and fragments can behave like invisible dandelion fluff, released from active growth areas [Condition 3], drifting through air currents, settling elsewhere [Condition 2], and potentially causing health effects even in spaces with no visible mold." — Schrantz et al., 2025
One of the most important concepts in the paper is what they call the building as a system — and it maps directly onto what we call the stack effect in building science. Air moves from high-pressure zones to low-pressure zones, continuously, through every crack, cavity, penetration, and connection in the building assembly. A crawlspace under negative pressure draws air upward from the soil and pushes it into the living space. An attic with poor sealing at the ceiling plane pulls conditioned air up from below and exchanges it with attic air. HVAC systems that run through contaminated spaces distribute whatever is in those spaces throughout every room.
This is why I have always said that knowing remediation before knowing inspection makes the difference in how you approach a property. If you have only learned to identify and treat visible mold, you are treating symptoms. If you understand how the building breathes — where the pressure differentials are, which direction air moves, which cavities are connected to the living space — you can find the contamination pathways before you build a scope. You know which reservoirs matter and which ones will recontaminate the living space after everything else is cleaned.
The paper cites Dr. Joseph Lstiburek of Building Science Corporation directly on this point: air moves from high-pressure to low-pressure zones, dragging moisture, particulates, and biological contaminants with it. A failure to map those pressure-driven flows is a failure to accurately diagnose the building. And a diagnosis that misses the contamination pathway will produce a scope that does not solve the problem.
The paper is direct about the limitations of the most commonly used testing method: the air spore trap. A spore trap captures a five-to-ten-minute snapshot of airborne particles. Results are heavily influenced by whether anyone has been moving through the space, where the sampler is placed, and whether the HVAC is running. More importantly, spore trap analysis can only identify organisms to the genus level, not the species level — meaning the analyst cannot speciate Aspergillus and Penicillium at all, since those two genera covering more than 900 species are morphologically identical under a microscope. Every Aspergillus and Penicillium counted on a spore trap is counted as an undifferentiated group, regardless of which specific species it is and what health implications it carries.
The more powerful tool is DNA-based dust analysis using MSQPCR — Mold-Specific Quantitative Polymerase Chain Reaction. Unlike spore traps, MSQPCR analyzes settled dust, identifies molds to the species level regardless of whether they are viable or dead, and detects the DNA associated with 300 to 1,000 fungal fragments per species — the microscopic particles that spore traps miss entirely. The paper is explicit: for a thorough assessment of a water-damaged building, there is no substitute for MSQPCR dust sampling. Spore traps have a role, but as a complementary method, not a primary one.
Why "passed" air tests can mean nothing
An air spore trap captures a five-minute airborne sample. It cannot identify species, cannot detect non-viable fragments, and cannot tell you what is settled in the dust, embedded in the insulation, or distributed through the ductwork. A clean air sample in a room with contaminated dust, insulation, and HVAC components is a false negative — not a clearance.
One section of the paper that I want to highlight specifically deals with what is present in a water-damaged building beyond mold. Most people think about mold remediation as a mold problem. The paper is clear that the contamination picture in a seriously water-damaged building is broader than that, and includes two categories that standard mold remediation protocols rarely address.
Endotoxins are fragments of the outer membrane of gram-negative bacteria. They are potent inflammatory agents — tiny, submicron particles that aerosolize readily, settle into dust, and trigger immune responses in sensitive individuals. They are measured in Endotoxin Units using the LAL assay, a test that most remediation scopes never order. In a building that has had a sewage backup, significant water intrusion, or prolonged elevated humidity, endotoxin levels can be substantially elevated even after visible mold is removed.
Actinobacteria are filamentous gram-positive bacteria that thrive in moist, cellulose-rich environments — exactly the conditions found in water-damaged drywall, insulation, and wood framing. They have been documented in cases of hypersensitivity pneumonitis and building-related illness. They cannot be reliably captured by standard culture methods and require DNA-based sequencing for accurate identification. Most remediation contractors have never considered them as part of the contamination picture. They are there nonetheless.
The practical implication: a building assessment and remediation scope that only addresses mold — even a well-executed one — may leave other biologically active contaminants in place. For a typical occupant, that may be acceptable. For someone with an immune condition, an autoimmune diagnosis, or unusual sensitivity to their environment, it may not be.
The paper has an entire section on sequencing — the order in which assessment and remediation steps happen — and it aligns directly with how I approach every project. Order matters. Doing steps out of sequence produces worse outcomes than doing the same steps in the right order, even if the individual work quality is identical.
The paper gives a concrete example: recommending HVAC cleaning after whole-home particulate remediation can reintroduce contaminants and undermine everything that was just cleaned. The HVAC has to be addressed before or simultaneously with the living space, not after. Similarly, failing to prioritize the crawlspace early in a project compromises the downstream cleaning of the living space above it because the pressure flow from the crawlspace continues to push contaminated air upward throughout the work.
In my practice, every scope starts with the building's contamination pathways — where is the source, where is it moving, what is the sequence that cuts off the supply before addressing the distribution. In a standard home with a crawlspace, attic, and HVAC system, that almost always means crawlspace first or simultaneous with the primary remediation zone. It means HVAC isolated and evaluated before the living space is cleared. It means the clearance verification is done in the right order with the right testing method after all work is complete — not a spore trap run in one room while the crawlspace and attic are still untouched.
The paper argues for a language shift that I think reflects something real: the word "remediation" implies correcting a specific deficiency. It has come to mean, in practice, removing visible growth and calling the job done. The term "environmental restoration" implies something more comprehensive — not just removing contamination but correcting the failures that caused it, addressing what is hidden and subvisible, and returning the building to a genuinely healthy baseline.
That distinction matters for how a project is scoped and what the homeowner is told at the end. A remediation job that removes visible growth, treats the structural surfaces, and runs an air test is not the same as an environmental restoration that traces the contamination pathway, corrects the moisture source, addresses the secondary reservoir in the attic or crawlspace, and verifies clearance using a testing method that actually detects what is present. Both might be called "mold remediation." They are not the same thing, and the health outcomes for a sensitive occupant are very different.
The paper also calls out the spray-and-walk-away approach directly — the persistent industry tendency to apply biocides to mold growth as if that constitutes remediation. It does not. The authoritative guidance — including IICRC S520 — has long recommended against relying on chemical biocides in place of physical removal and source control. Dead mold fragments are still biologically active. Spraying a fungicide does not remove the material, does not address the reservoir, and does not restore the building's fungal ecology to Condition 1.
The spray-and-pray problem
Applying a biocide to mold growth does not remediate it. Dead mold fragments are still biologically active and still trigger immune responses in sensitive individuals. The only effective treatment is physical removal of the contaminated material combined with thorough cleaning of the structural surfaces — not a chemical coating applied on top of the problem.
The research paper is written for industry professionals, but its conclusions translate directly into what a homeowner should know when evaluating their situation. Here are the practical takeaways:
Visible inspection is a starting point, not a conclusion. If an inspector looks around and tells you there is nothing to worry about because they do not see visible mold, that is an incomplete assessment. The most significant contamination in a water-damaged building is often not visible — it is in hidden cavities, inside insulation, behind assemblies that conceal it, and distributed through the building as settled particulate.
The building functions as a system. A crawlspace problem is not contained to the crawlspace. An attic with biological staining is not contained to the attic. Air moves through the building continuously, carrying particulates from one space to another. An assessment that does not trace those pathways — that evaluates rooms in isolation without understanding the pressure dynamics of the full structure — will miss the sources that matter most.
Clearance testing matters as much as the remediation work. An air test taken immediately after cleaning, before the building has equilibrated, does not tell you whether the remediation was successful. A valid clearance requires the right testing method — one capable of detecting what is actually present — applied at the right time in the right sequence, after all remediation work including the HVAC evaluation is complete.
For sensitive occupants, the standard matters more. Someone without a significant health condition can tolerate a building that has been reasonably well remediated even if some residual contamination remains. Someone with an immune condition, who has been sick for months, or who reacted strongly during the original exposure, needs a genuinely higher standard of environmental restoration. The research is clear that what is "good enough" for a typical occupant is often not sufficient for someone in that category — and that knowing the difference is the job of a qualified inspector, not a sales pitch.
Think your building might be more than a simple mold problem?
Anthony Denatala has 20+ years in remediation before inspection — which means he understands how buildings contaminate themselves and how to trace it. CMRS certified. Forensic inspection with written findings. Greater Atlanta.
Source: Schrantz, M., Banta, J., Schwartz, L., Lark, D. (2025). Built Environment as a Dangerous Ecosystem. Medical Research Archives, Vol. 13, Issue 8. European Society of Medicine. · IICRC S520 Standard for Professional Mold Remediation, 4th Ed. · EPA Indoor Air Quality — Mold Resources
