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MOLD: A COMPLETE GUIDE to TEST CLEAN PREVENT
AIR CLEANER PURIFIER TYPES
AIR FILTERS for HVAC SYSTEMS
AIR POLLUTANTS, COMMON INDOOR
AIR QUALITY IMPROVEMENT STRATEGIES
ALLERGEN TESTS for BUILDINGS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ODORS IN BUILDINGSS
ATTORNEYS and EXPERT WITNESSES
BIBLIOGAPHY ENVIRONMENTAL HEALTH, MOLD, IAQ
CAR MOLD CONTAMINATION
CARPET DUST IDENTIFICATION
CARPET MOLD CONTAMINATION
CAT DANDER in BUILDINGS
COMBUSTION GASES & PARTICLE HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
CPSC Indoor Air Pollution Book Online Copy
DUCT SYSTEM & DUCT DEFECTS
EMERGENCY RESPONSE, IAQ, GAS, MOLD
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOODS IN BUILDINGS-mold
GAS EXPOSURE EFFECTS, TOXIC
HUMIDITY CONTROL & TARGETS INDOORS
HOUSE DUST ANALYSIS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
MILDEW REMOVAL & PREVENTION
MOISTURE CONTROL in BUILDINGS
MOLD GROWTH on SURFACES, TABLE OF
MYCOPHOBIA, STAINS MISTAKEN for MOLD
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURES
OZONE for MOLD OR ODORS
RADON HAZARD TESTS & MITIGATION
SAFETY HAZARDS GUIDE
SICK HOUSE IAQ QUESTIONNAIRE
SMELL PATCH TEST to Track Down Odors
STAIN DIAGNOSIS on BUILDING INTERIORS
VENTILATION in BUILDINGS
Age of mold contamination in buildings: This article discusses how we assess the activity or inactivity of mold contamination in a building, what difference that means (or does not) in risk to building occupants, and how we can find evidence suggesting that a given mold contamination case is new, old, or includes both old and new fungal growth.
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Would you please let me know how an individual (or lab) would test for whether a mold found on attic sheathing is active vs. inactive?
Research on-line has told me the test for active vs inactive is whether it smears when you rub it. Is there a more technical test that can be done? Should a lab be able to tell me this when I supply a sample? - M.O.
The question of how we determine whether or not mold in a test sample is "active" is a bit misleading, although some surface test samples of mold do indeed give compelling evidence of recent active fungal growth. Our site photograph of moldy roof sheathing (above left) is an example. Is this mold growth "active" or "inactive", and does activity make much difference in risk to building occupants?
At MOLD AGE - Old is the Mold? we discuss visual clues that help determine the age of mold contamination in buildings or on building surfaces. There we explain what dried, desiccated, "old" mold growth may look like on a surface, in a test sample, and under the microscope. Among other factors, we distinguish between
Often we can confirm recent fungal growth in a tape sample by the presence of certain growth structures, hyphal buds, or even the state of a conidiophore.
Our photo of Epicoccum sp. fungal spores and hyphae (above left) collected from a building surface shows intact, fragile hydrated complete spores still connected to hyphae - this mold growth is recent and might indeed be considered "active mold growth" as would the intact, hydrated, and budding Aureobasidium pullulans spores shown in our second lab photo (above right). This burst of Pleospora spores is clearly active. Similarly, for certain species that produce long fragile spore chains, the presence of long mold spore chains is certainly indicative of nearby active fungal growth, as these chains break up rapidly into individual spores when airborne.
Conversely, highly-dessicated, fractured, or damaged fungal material that lacks budding hyphae or sporulating intact conidiophores are almost certainly "inactive" mold growth in the spot where sampled.
Watch out: "mold activity" or "mold inactivity" can be misleading conclusions about the risks associated with mold growth in buildings.
The moldy books in a college library (photo at left) were in the opinion of some people "an old inactive mold problem" but when workers began dehumidifying the area in preparation for a mold cleanup, visible clouds of Aspergillus sp. spores were released into the air by small air currents caused by simply walking down the aisle between stacks of books.
Watch out however: using a swab or culture test for "viable mold" in buildings can give very misleading results since what grows in the culture is what likes the culture, not necessarily what is present or dominant in the building. See MOLD TESTING METHOD VALIDITY and in particular Mold Culture Plate Test Errors.
These reasons explain why in addition to testing to confirm the presence of mold growth, and to confirm that it is not simply cosmetic, in cases of possibly costly mold cleanup or diagnosing a possible building contribution to indoor air quality complaints, is important to have an expert perform a competent inspection of the building.
As we explain at MOLD AGE - Old is the Mold?, especially in older buildings where there has been a recent sudden leak event associated with mold growth, it is often possible to identify pre-existing mold as well as mold-producing conditions. In unambiguous cases, the "new" mold associated with the building leak event may, by luck, appear in a limited area of the building which maps the area wet by the recent leak, and separated by distance or building area from other moldy areas which in turn are associated with other building leaks or conditions. The physical separation of wet areas and wet conditions may be sufficient to make a clear assignment of mold causation in such cases.
In ambiguous cases, there is fresh, active fungal growth, probably associated with a recent leak or flooding event in the building, which has grown entirely or partly overlapping pre-existing mold growth. In this case the assignment of cause and age of mold in the building can be ambiguous. If an insurance claim is involved, insurance company policy details and internal claims adjustment guidelines will determine the extent to which insurance coverage will address building remediation and repair for these overlapped-occurrence mold conditions.
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