How to Determine Mold Risk Levels in Buildings: Based on Visual Inspection
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- How to Determine Mold Risk Levels in Buildings Based on Visual Inspection
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To assist in predicting the chances and degree of mold contamination in buildings, even when extensive mold is not visible,
this document describes four levels of risk of existing mold contamination or future mold
growth in buildings based on the building history, visual observations, and the
materials of construction.
Additional risk factors that need to be considered in deciding if a professional mold/IAQ
investigation is warranted must include the health risk or vulnerability of building occupants
and the existence of complaints at a building.
Also see
"When to hire a professional to investigate a building for toxic mold."
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Characteristics of Buildings or Building Areas at Very-Low Mold Risk: Mold Risk Level 1
To assist making decisions regarding building cleaning where mold is a
concern, and considering that quantitative measures of "levels of
mold" may be precise but highly inaccurate, and considering that
quantitative measures used alone fail to adequately consider the results of a
thorough, expert visual inspection, building history, and/or visual evidence of
mold risk factors, I have invented four subjective levels of risk of actionable
mold contamination.
These include areas and materials in a building for which there is no evidence of having
become wet or exposed to high moisture, where no problematic mold has been
detected, or where the materials are generally unfriendly to mold growth,
such as clean, un-painted masonry surfaces. Mold can appear in these areas
in the future if building conditions change or a new mold-related event
occurs. Where a building is at risk-level 0, invasive inspection and
expert mold testing are not required.
Characteristics of Buildings or Building Areas at Low Mold Risk: Mold Risk Level 2
These include areas with the presence of
mold-friendly building materials such as drywall and kraft-faced
insulation do not appear to have been wet, but they are present in
enclosed cavities (such as walls or ceilings) with evidence that nearby
building areas have been wet or moldy, exposing the Level 1 areas to high
moisture levels.
This category also includes instances where mold-friendly
materials have become wet from a single event and where the materials were
successfully and completely dried within 24 to 48 hours of becoming wet,
leaving no hidden, enclosed cavities unattended.
Mold is not visible and mold has not been detected by expert inspection
and sampling. In the absence of mold-related occupant complaints expert
inspection and testing are not required.
Characteristics of Buildings or Building Areas at High Mold Risk: Mold Risk Level 3
These include areas with the presence of mold-friendly building materials such as drywall and kraft-faced
insulation are wet or have been wet, and these materials remain in place
in enclosed cavities (such as walls or ceilings) with no evidence that the
cavities were completely dried out within 24 to 48 hours after the wetting
event, or with evidence that wetting has been a recurrent event.
Additional inspection and testing may be appropriate and may require use
of invasive methods.
Characteristics of Buildings or Building Areas With Actionable Mold Contamination: Mold Risk Level 4
These include areas with the presence of non-cosmetic mold (potentially allergenic, toxic, or pathogenic) has been
found in an indoor area. (Cosmetic mold does not require special treatment and should be
identified so as to avoid inappropriate costs.)
Areas smaller than 30 sq.ft.
can usually be cleaned or removed without
requiring expert testing and remediation services. Non-cosmetic indoor
mold found covering 30 sq.ft. or
more of contiguous or effectively-contiguous space means that professional
cleaning and possibly professional diagnostic inspection and testing are
appropriate.
Cosmetic molds such as bluestain are of no risk to the
building or its occupants and should be addressed only if it is a cosmetic
concern. See Recognize Harmless Black Mold for details.
Expert sampling may suggest that significant problematic mold is
present at an uncertain level/extent in the building, or mold may not have
been detected. Additional inspection and testing are appropriate and may
require use of invasive methods.
More expert information on this topic
More Information on Building Diagnostic Inspections and Repairs
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