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mobile guide to mold in buildingsMobile View
ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY

MOLD: A COMPLETE GUIDE to TEST CLEAN PREVENT

ACCEPTABLE MOLD LEVEL
ACCURACY OF VARIOUS MOLD TEST METHODS
ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD
ACTIVITY of MOLD in buildings
AGE of MOLD - Old is the Mold?
AIR TEST FOR MOLD: ACCURACY
AIR TEST SAMPLING CASSETTE STUDY
AIRBORNE MOLD SPORE COUNT ACCURACY
AIRBORNE PARTICLE ANALYSIS METHODS
ALLERGEN TESTS for buildings
ATTORNEYS and EXPERT WITNESSES
ATTIC MOLD

BASEMENT MOLD
BASEMENT MOLD WATER IMPACT
BATHROOM MOLD
BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ
  Bacteria, Mold, & Pollen
  Microscopy, Microchemistry
  Basic Science & Theory
  Building Science & Industrial Hygiene, Field & Lab Methods
  Environmental Hazards, Consumer Publications
  METHANE GAS SOURCES
  MOLD ATLAS & PARTICLES INDEX
  MOLD CLINICAL REFERENCE TEXTS
  MOLD FAQ's
  MOLD RELATED ILLNESS GUIDE
  MOLD RELATED ILLNESS List
BIOLOGICAL POLLUTANTS
BLACK MOLD, HARMLESS COSMETIC
BLACK MOLD, TOXIC & ALLERGENIC
BLEACHING MOLD, Advice about
BOOK MOLD, Moldy Book Cleaning
BOOKSTORE - ENVIRONMENTAL
BROWN HAIRY BATHROOM MOLD

CACTUS FUNGI / MOLD
CAR MOLD CONTAMINATION
CARPET DUST IDENTIFICATION
CARPET MOLD CONTAMINATION
CARPET PADDING ASBESTOS, MOLD, ODORS
CARPET FUNGICIDAL SPRAY
CARPET STAIN DIAGNOSIS
CARPET & other STAIN TESTS
CARPET TEST PROCEDURE
CARPETING & INDOOR AIR QUALITY
CHAIN OF CUSTODY - TEST SAMPLE
CLEARANCE INSPECTIONS - MOLD CLEANUP
CRAWL SPACES
  CRAWLSPACE MOLD ADVICE

DIRECTORY of MOLD / ENVIRONMENTAL EXPERTS
DIRT FLOOR MOLD CONTAMINATION
Disinfectants
Disinfecting Buildings with Bleach
DRYWALL MOLD

DUCT SYSTEM & DUCT DEFECTS
DUST ANALYSIS for FIBERGLASS
DUST CONTAMINATION FROM HVAC?
DUST SAMPLING PROCEDURE

EFFLORESCENCE, Salts & White / Brown Deposits
EMERGENCY RESPONSE, IAQ, GAS, MOLD

FEAR of MOLD - MYCOPHOBIA
Fiberboard Insulation Sheathing Mold
FIBERGLASS INSULATION MOLD
FIBERGLASS PARTICLE CONTAMINATION TEST
FIELD INVESTIGATION SERVICE
FIND MOLD, ESSENTIAL STEPS
FIND MOLD in BUILDINGS, HOW TO
FIRE DAMAGE vs MOLD DAMAGE
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOODS IN BUILDINGS-mold
FLOORING MATERIALS, Age, Types
FUNGICIDAL SPRAY & SEALANT USE GUIDE

GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION & MEASUREMENT

HOUSE DUST ANALYSIS
HOUSEWRAP AIR & VAPOR BARRIERS
HIDDEN MOLD, HOW TO FIND
HUMIDITY CONTROL & TARGETS INDOORS

INDOOR AIR HAZARDS TABLE
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INDOOR AIR QUALITY IMPROVEMENT GUIDE

INSULATION INSPECTION & IMPROVEMENT
INSULATION MOLD
  Mold in Fiberglass Insulation
  Mold on Books, Book Conservation
  Mold on Fiberboard Insulating Sheathing
  MOLD PREVENTION AFTER FLOODING
  MOLD RESISTANT CONSTRUCTION
  Mold in Foam Insulation
  Moldy insulation may look clean
  Why does mold grow in fiberglass?
  When to test insulation for mold
  How to Test for Mold in Insulation
  References, Fiberglass Hazards
  Vacuuming exposed insulation

ITCHY FABRICS

LABORATORY SERVICES
LAB PROCEDURES MICROSCOPE TECHNIQUES

MEDIA BLASTING for MOLD REMOVAL

MICROSCOPE DIGITAL PHOTOGRAPHY
MICROSCOPE SLIDE PREPARATION
MICROSCOPE SLIDE PREP - PERMANENT MOUNTS
MICROSCOPE TECHNIQUES for the LAB

MEDIA BLASTING for MOLD REMOVAL
METHANE GAS SOURCES
MICROSCOPE DIGITAL PHOTOGRAPHY
MILDEW in BUILDINGS ?
MILDEW ERRORS - MOLD PHOTOS
MILDEW REMOVAL & PREVENTION
MOISTURE CONTROL in BUILDINGS

MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD
MOLD ACTIVITY in buildings
MOLD AGE - Old is the Mold?
  Single-leak mold
  Multi-event mold
  Mycologists' view on age of mold
  Building scientists' view on age of mold
  Conditions affecting fungal growth
  Conditions permitting mold age assessment
  Determine if Mold Contamination is Active?

MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
  Black Mold
  Brown Mold
  Green Mold
  Red Mold
  Yellow Mold
  White Mold
  Invisible Mold
  Meruliporia Mold Photographs
  Mildew Photographs
  Recognize Cosmetic Mold
  Recognize Harmless Black Mold
  MOLD GROWTH ON SURFACES, PHOTOS

MOLD APPEARANCE - STUFF THAT IS NOT MOLD
  HARMLESS INDOOR PARTICLES
    Black stains from soot/thermal tracking
    Black stains from animals
    Black cosmetic mold
    Efflorescence & white or brown deposits
    House dust
    MYCOPHOBIA, STAINS MISTAKEN for MOLD
    Pollen
    Sprayed foam insulation
    White stuff that is not mold
    Wood sap

MOLD ATLAS & PARTICLES INDEX
MOLD by MICROSCOPE
MOLD in the PETRI DISH, PHOTOS
Mold on Books, Book Conservation

MOLD CLASSES, HAZARD LEVELS

MOLD CLEANERS - WHAT TO USE
MOLD CLEANUP COMPANIES
MOLD CLEANUP, DO IT YOURSELF
MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD
MOLD CLEANUP - BLEACH
MOLD CLEANUP - HEALTH RISKS
MOLD CLEANUP - LIMITATIONS
MOLD CLEANUP - MISTAKES to AVOID
MOLD CLEANUP - MEDIA BLASTING
MOLD CLEANUP - SAFETY WARNINGS
MOLD CLEANUP - WOOD FLOORING
MOLD CLEANUP - WOOD FRAMING & PLYWOOD

MOLD CLEARANCE INSPECTIONS
MOLD CLEARANCE: FOLLOWUP STEPS

MOLD CLINICAL REFERENCE TEXTS

MOLD CONSULTANTS/INSPECTORS

MOLD CONTAMINATION LEVELS

MOLD CULTURE PHOTOS
MOLD CULTURE SAMPLING METHOD
MOLD CULTURE TEST ERRORS
MOLD CULTURE TEST KIT VALIDITY

MOLD DETECTION & INSPECTION GUIDE
MOLD DOCTORS - ENVIRONMENTAL MEDICINE

MOLD or INDOOR AIR EMERGENCY RESPONSE
MOLD EXPERT, WHEN TO HIRE
MOLD EXPOSURE, FOOD HAZARDS
MOLD EXPOSURE RISK LEVELS
MOLD EXPOSURE STANDARDS

MOLD FAQ's
MOLD FREQUENCY in buildings
MOLD GROWTH ON SURFACES, PHOTOS
MOLD GROWTH on SURFACES, TABLE OF
MOLD GROWTH in/on BUILDING INSULATION

MOLD INFORMATION CENTER
MOLD INSPECTORS & MOLD TESTERS
MOLD INSPECTION HOME BUYERS GUIDE
MOLD INSPECTION SERVICE
MOLD INVESTIGATION PROCEDURE TIPS
MOLD INVESTIGATION REPORTS

MOLD KILLING GUIDE
MOLD LAB REPORTS

MOLD LEVEL IN AIR, VALIDITY
MOLD LEVEL REPORTS
MOLD LEVELS IN buildings
MOLD by MICROSCOPE
MOLD ODORS, MUSTY SMELLS
MOLD on or in CARPETS
MOLD ON DIRT FLOORS

MOLD PREVENTION GUIDE

MOLD RELATED ILLNESS GUIDE
MOLD RELATED ILLNESS SYMPTOMS
  Types of Mold Reactions
  Alphabetic List of Mold Symptoms
MOLD RESISTANT CONSTRUCTION

MOLD SAFETY WARNINGS
MOLD SPRAYS, SEALANTS, PAINTS

MOLD STANDARDS
MOLD STANDARDS - GOVERNMENT
MOLD STANDARDS - WORLD WIDE

MOLD TOXICITY VARIATION

MOLD TEST KITS for DIY MOLD TESTS
MOLD TEST PROCEDURES
MOLD TEST REASONS
MOLD TESTING METHOD VALIDITY
MOLD TESTING SERVICES

MSDS Material Safety Data Sheets
MSDS Material Safety Data Sheets
MVOCs & MOLDY MUSTY ODORS
MYCOPHOBIA, STAINS MISTAKEN for MOLD
MYCOTOXIN EFFECTS of MOLD EXPOSURE

ODORS GASES SMELLS, DIAGNOSIS & CURE
OZONE for MOLD OR ODORS

PAINTS & COATINGS ODORS IN buildings

RENTERS & TENANTS GUIDE TO MOLD
ROBIGUS & Wheat Rust Fungus
ROT, TIMBER FRAME

SLIDE PREPARATION, MICROSCOPE
SMELL PATCH TEST to Track Down Odors
SOUND CONTROL in BUILDINGS
STAIN & BIODETERIORATION AGENT CATALOG
STAINS on BUILDINGS - QUICK GUIDE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
STAINS on INDOOR SURFACES: PHOTO GUIDE
STAINS & Thermal Tracking

TECHNICAL & LAB PROCEDURES
TRAPPED MOLD BETWEEN WOOD SURFACES

VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in buildings
VINYL Siding or PLASTIC Window ODORS in buildings
VINYL CHLORIDE HEALTH INFO

WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in buildings
World Trade Center Collapse Dust Photos

More Information

Aspergillus niger (C) Daniel Friedman

How to Estimate the Activity of Mold Contamination in buildings
InspectAPedia®  -      

  • MOLD ACTIVITY? How to evaluate mold samples for indications of active mold growth
  • Does it matter whether or not building mold growth is "active?
  • How to Estimate the Age of Mold Contamination in buildings
  • Evidence of Mold History in buildings
  • Evidence of Mold Age in Laboratory Samples
  • Questions & answers about how to determine the age of mold growth or contamination in buildings or on building surfaces

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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Determining Whether or Not a Mold Test Sample Shows Active Mold Growth

Readers should also see MOLD AGE - Old is the Mold?. Also see MOLD GROWTH on SURFACES for an index of what mold genera/species are frequently found on various building surfaces and materials.

Moldy roof sheathing (C) Daniel FriedmanQuestion: how do we determine whether or not mold in a building is active vs. inactive?

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.

Answer:

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

  • Dry desiccated fungal material is consistent with prior, currently inactive fungal growth on the surface which was sampled. Very desiccated sample materials are almost certainly not indicators of active current fungal growth.
  • Fresh, hydrated fungal hyphae or fungal fruiting bodies (conidiophores or other sporulating bodies) are consistent with ongoing, current fungal growth. Some fungal bodies such as thick woody structures grow much more slowly and if present, almost certainly have been developing over a long time.
Aspergillus niger (C) Daniel Friedman Aureobasidium pullulans (C) Daniel Friedman

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.

Moldy books (C) Daniel Friedman

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.

  1. Mold test sample size: Because a sample represents a small area of a building and of time, and because other materials may be present that the sampler did not see, detect, or test, a single sample is an indicator, not a conclusion about a building's condition.
  2. Multiple mold genera/species: Next, the conditions that produced fungal growth that was seen and tested mean that building conditions were ripe for mold growth, perhaps on other surfaces or in cavities or in less visible locations. For example we may see one species of mold on an attic roof underside, say Cladosporium cladosporioides, perhaps even desiccated by the heat of sun beating on the roof, while the conditions that produced that growth also produced a non-visible but more troubling Aspergillus sp. contaminating growth in building insulation in the attic floor. So at a given time, some mold on building surfaces may be "inactive" while nearby another genera/species may be growing like mad, or releasing spores like mad, i.e. "active".
  3. Dead toxic mold: Next, we suspect an underlying faulty premise that the salient question is whether or not a fungal growth is active or not in a building. In fact even currently inactive (no apparent recent fungal propagation) fungal presence on a surface can be a hazard since spores and fungal hyphal fragments may be toxic, pathogenic, or allergenic even in that state. That point remains true even if some misinformed "mold remediator" tries to "kill" the fungus with a fungicide or bleach.
  4. Smearing mold?: Further, he claim that smearing mold with a finger determines whether or not it is active or not is nonsense. A mold growth on a surface could be very desiccated and may not have actively propagated for a long time but still can be "smeared" with a finger wipe. But we agree that if you cannot smear suspected-mold or better, if you cannot obtain particles on an adhesive tape sample, then the surface may have been previously cleaned, and what remains may be no more than a cosmetic stain.
  5. Inoculation of mold: Finally, even if mold is "not actively growing" at the time that a sample is obtained from a surface (or in dust or air), the presence of a large amount of fungal material in a building can lead to rapid mold re growth and propagation when building conditions change to those more conducive to growth of the fungi already present.

    All mold is everywhere all the time in the form of spores ready to inoculate a material or surface. So when building conditions are ripe for mold growth, it is likely to occur. Predominantly, it is the building conditions that determine whether or not we will have a building mold problem, not the presence or absence of mold in general. But the presence of a large reservoir of pre-existing (inactive) mold can speed both the recurrence and the extent of a future mold contamination. "Inactive" does not mean "non-viable".

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.

Questions & Answers regarding this article

Questions & answers about how to determine the age of mold growth or contamination in buildings or on building surfaces

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Technical Reviewers & References

  • InspectAPedia.com® - Daniel Friedman - Publisher & Editor.
  • InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
  • Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
  • Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD
MOLD ACTIVITY in buildings
MOLD AGE - Old is the Mold?
  Single-leak mold
  Multi-event mold
  Mycologists' view on age of mold
  Building scientists' view on age of mold
  Conditions affecting fungal growth
  Conditions permitting mold age assessment
  Determine if Mold Contamination is Active?
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
MOLD APPEARANCE - STUFF THAT IS NOT MOLD

  • Thanks to reader Mike Olsen for discussing the problem of how a lab can determine whether or not mold in a test sample is active or inactive - June 2010

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
  • Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
  • Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
  • Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
  • "A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
  • US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
  • US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
  • "A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
  • "Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
  • "Disease Prevention in Home Vegetable Gardens," Patricia Donald, Department of Plant Microbiology and Pathology, Lewis Jett
    Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
  • "Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
  • Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
  • Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-
  • US EPA: Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
  • Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
  • ...

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