Photograph of moldy basement ceiling before cleaning.

Photograph of a basement ceiling after cleaning by media blasting.

How to Clean or Remove Toxic Mold in buildings - A Homeowner's or Apartment Owner's Guide

Here is a step by step guide on what to do about mold in a building
- How to clean or remove mold properl
Questions & Answers about the best procedures to get rid of mold and mold smells in buildings
References

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This article describes how toxic or allergenic mold is removed from buildings - mold cleanup, or mold remediation. We discuss how to physically remove problem mold (don't just spray over it), what cleaners can be used for mold removal, and use of bleach in mold cleanup and removal jobs. We also list related mold cleanup or remediation articles that address special problems such as mold odors, mold removal from irregular surfaces, and stains or odors on roofs or in cars. This is article is part of our series starting at ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD, a document which provides an easy to understand step-by-step guide for dealing with toxic or allergenic indoor mold and other indoor contaminants: what to do about mold.

The steps in this document will be sufficient for many building owners who want to do their own mold investigation, mold testing, mold cleanup, and mold prevention in their home or office. Readers should also see MOLD CLEANUP with BLEACH and MOLD CLEANUP - WOOD FRAMING & PLYWOOD and also MOLD CLEANUP - MISTAKES to AVOID. Also see see TRAPPED MOLD BETWEEN WOOD SURFACES for a discussion of the question of need to remove mold from mated and inaccessible building surfaces.

How to Clean or Remove Mold, Moldy Debris, Other Indoor Environmental Contaminants - a Homeowner's Guide

Please see ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD for a detailed procedure on mold cleanup in buildings. What follows below is a succinct guide to mold cleanup for homeowners or tenants. Renters may also want to see RENTERS & TENANTS GUIDE TO MOLD & INDOOR HAZARDS.

Protect the occupants and yourself from mold, demolition dust, debris, cleaning chemicals, etc. Where a large area of cleanup is involved (more than 30 sq.ft.) a professional is usually called to establish negative air in the work area and to install containment barriers of plastic or other material to protect cleaner areas of the building from cross-contamination during the cleanup.

If you used a building environmental specialist to inspect and define the scope of work, you should have baseline mold test samples of both the work area and other building areas which will permit you to state definitively, at the end of the cleanup, whether or not the cleanup has caused cross-contamination of other building areas.

The spotless cleaning produced for the second photo above was obtained by using a professional who used media blasting to clean these surfaces. Such measures may be needed for large or complex surfaces, but quite often the necessary steps are less technical and less onerous, as we describe next.

Clean or remove mold and moldy debris: The most succinct Mold Remediation or Mold Cleanup Guidelines one could state would be this: the objective is not to sterilize your environment or "kill" mold, steps which are ineffective anyway - the operative words are "clean" or "remove" problem mold and then to correct its cause.

If the total square feet of moldy material is less than 30 sq.ft. it is reasonable to handle the mold cleanup as an ordinary building cleaning or renovation procedure - hiring experts to establish negative air, dust containment, etc. is not required, but you should still take steps to minimize cross contamination in the building and to protect yourself and other occupants from moldy dust and debris.

If the total contiguous square feet of moldy material is large (more than 30 sq.ft.) then you should consult a professional to inspect the building, find all of the problem mold areas, and to prepare a mold cleanup or mold remediation plan which will guide the mold remediation company (who should be a totally independent contractor in order to avoid conflicts of interest).

The mold consultant should also advise on the steps needed to prevent future mold growth - fix the causes of mold contamination. If the mold cleanup is a costly project you should have the independent mold consultant perform a thorough visual and physical inspection of the building after the mold cleanup to assure that it was effective.

Note: some sources have amended the 30 square feet rule to 10 square feet as the size suitable for homeowner cleanup.

Remove and dispose of moldy items that cannot be effectively cleaned: Moldy drywall, paneling, trim, carpets, boxes, junk, are removed and disposed-of as construction debris or trash, either because the item cannot be effectively cleaned, or in some cases because the cost of cleaning exceeds the value of the object. Be sure to remove building insulation that has been wet or smells moldy or has been exposed to high levels of airborne mold. See INSULATION MOLD.

Usually moldy drywall and other debris can be disposed-of as ordinary construction debris or trash.

Scrubbing moldy surfaces - no sprays, no ozone, no sterilization: We're talking about scrubbing here. It's the physical removal of moldy or allergenic debris that's important, not the surface sterilization. The second we permit someone to "spray for mold" we can count on them to fail to do an adequate mold cleanup.

And if the moldy surface to be cleaned is "cleanable" so irregular or inaccessible as to make physical wiping or scrubbing impractical, you may want to consider MEDIA BLASTING for MOLD REMOVAL. The photos at the top of this page show the results of media blasting moldy wood surfaces.

What to Use to Clean Off Mold from Building Surfaces, Contents, Items

What to use to clean off mold from all of the exposed hard, cleanable surfaces: to clean off a moldy surface, you could use simple clean water, soapy water, spray cleaners, or if you prefer, a commercial biocide (follow their directions) or a dilute bleach cleaning solution. But because so many readers have asked about specific mold "cleaning" or mold "killing" methods we list and comment on these approaches below.

At MOLD CLEANERS - WHAT TO USE we provide a detailed description of different methods people use to "clean off" or "kill" mold.

How to Use Bleach to Clean Up a Moldy Surface

Bleaching or "killing" mold is not the objective. Bleach will not kill all of the mold anyway - we can tease viable spores out of lots of "bleached mold" samples we see in the lab.

The object of mold removal is to clean the surface, to remove loose moldy material, not to try to sterilize the surface. Certain mold-contaminated materials that cannot be cleaned (drywall, carpeting, curtains) should be discarded. Clothing and bedding linens or towels can be washed or dry-cleaned.

Keep that in mind. If you want to use bleach as a cleaning agent instead of other cleaners (soap and water would work just fine) here are some mold cleanup suggestions for homeowners from the Canadian Mortgage and Housing Corporation CMHC. Please see MOLD CLEANUP with BLEACH for details of how to mix and use bleach to clean a hard surface in a building as well as warnings about where bleaching mold is a cosmetic band-aid that just won't work.

Dilute bleach with one part household bleach to four parts of clean water (do not add other cleaners to this solution as you may accidentally cause the release dangerous chlorine gas)
Ventilate the work area
Wear rubber gloves and eye protection
After physically cleaning and removing all loose mold, dirt, debris, from the surface being cleaned, let the solution stand on the surface for 10-15 minutes.
Rinse the cleaned surface thoroughly
Be sure that the cleaned surfaces are totally dry before restoring any building insulation, drywall, etc.
Discard moldy fabrics or other similar materials that cannot be surface-cleaned.

How to Deal With Other Mold-Related Problems

CAR SMELL - Mold DEODORIZING - mold in cars, campers, trucks, RVs can be caused by water leaks and can make a moldy smell problem that's hard to cure.
MEDIA BLASTING for MOLD REMOVAL - for very irregular surfaces, physical cleaning of mold can be cost-prohibitive; try media blasting
MOLD CLEANUP - MISTAKES to AVOID
MOLD PREVENTION GUIDE - make sure that your mold cleanup effort is not wasted by taking steps to prevent mold growth recurrence
ODOR DIAGNOSIS CHECKLIST, PROCEDURE - maybe that smell isn't mold?
ODORS, Smells, Gases in buildings-Diagnosis & Cure - how do we track down mold or other building smells to their source - necessary steps to correct odors in buildings.
OZONE for MOLD OR ODORS - warnings about using ozone treatments to try to "kill mold" or "remove odors" - there is a place for this equipment but not as a substitute for mold cleanup and overdone it creates more problems than it solves.
STAINS on & in BUILDINGS, CAUSES & CURES - some indoor stains like thermal tracking are often mistaken for "toxic black mold"
STAINS on ROOF SHINGLES - those black roof stains might be mold, but more often, algae or something else
WATER ENTRY in buildings - not much use in cleaning up mold contamination if you don't also fix its cause. Also see MOLD PREVENTION GUIDE

Frequently Asked Questions (FAQs)

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Canada Mortgage and Housing Corporation, CMHC, "Moisture and Air, problems and remedies, Householders Guide," NHA 5968, 1989, reprinted to 1995 cmhc-schl.gc.ca 800-668-2642. Cette publication est aussi disponible en francasi sus le tire: L'air et l'humidite - LNH 5969.
"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

Here are the Details on How to Clean Up or Remove Toxic or Allergenic Mold in buildings

Mold Cleaning Procedures & Mold Remediation Standards Guidelines

How to Clean Moldy Wood Framing & Sheathing How to clean/seal mold from/on exposed lumber or plywood subfloor or roof sheathing indoors - some suggestions based on our field and laboratory research
Mold Cleaning, Remediation, & Clearance Testing Standards
Building Floods - Steps to Clean and Prevent Mold Home Page - Advice on Cleaning Mold and Preventing Future Mold after a building flood
How to Find and Test For Mold in buildings A 'how to' photo and text primer on finding and choosing the right spots to test for mold in buildings
Media Blasting: Mold Removal by Media Blasting - A test report (complete article, with illustrations) on the effectiveness of baking soda media blasting for cleaning fungal contamination in buildings, Daniel Friedman, Dennis Melandro, originally published in Indoor Environment Connections, Rockville MD, June 2003
Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens.
Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
MN University of Minnesota - Fungal Abatement Safe Operating Procedure
NY New York City Mold Remediation Guidelines - Assessment and Remediation of Fungi in Indoor Environments

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.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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

Allergies, Allergens, Allergy Testing in buildings - References & Products

Air Conditioning System Blower Fans & Filters Cascading for Optimum Indoor Air Quality
Allergen Tests in buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
Atlas of Mold Related Illness Symptoms & Complaints - long list of both documented, studied mold related illness, and complaints ascribed to mold contamination or allergens in buildings
Cat Dander: how to inspect and test a building for past or current presence of cats, cat hair, cat dander, and cat allergens
Clinical Atlas of Mold Toxicity - An Online Description of Toxic, Pathogenic, Allergenic Fungi, Fungal Diseases
Fiberglass Insulation Contains Mold© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Mold Action Guide detailed guide on finding, removing, and preventing indoor mold contamination
Odors, Odor Detection, Smells, & Gases how to find and identify sources of noxious or toxic odors and gases
Other environmental risks, Our much longer list: Asbestos, carbon monoxide, electromagnetic fields, etc.
Ozone: The Use of Ozone Indoors for Control of Odors and Mold Removal in buildings: A Summary of Hazards and False Claims.
Pollen Allergens: identification, plant pollen and indoor air quality
Products to Reduce Mold & Allergy Problems to reduce indoor mold or allergen levels: air cleaners, air purifiers, dust mite covers, vacuum cleaners, crawl space vents
Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
Rodent control issues, including dander, fecal, and urine contamination of buildings and Building insulation are discussed at our
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Action Guide: What to do about mold, mildew, and other indoor allergens
...

Mold Contamination Testing, Cleanup, Prevention: references & products

The Mold Information Center: What to Do About Mold in buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Aerobiology, Building Science, Microscopy, & Laboratory References, an extensive technical bibliography
Allergens: what they look like in buildings
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon) - The Atlas of Clinical Fungi is also available on CD ROM
Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
Clinical Mold References - Detailed bibliography of mold reference texts
"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
Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Fiberglass: Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
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-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
Looking for Mold Procedure: what mold is often found where in buildings - simple technical presentation
Meruliporia: the house eating fungus or "poria"
Mold Action Guide: Step-by-Step Instructions, What to do about mold, mildew, and other indoor allergens
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE Photos of what mold looks like in buildings
MOLD APPEARANCE - STUFF THAT IS NOT MOLD Photos of NOT-mold material that is sometimes mistaken for mold
MOLD ATLAS & PARTICLES INDEX, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
MOLD BY MICROSCOPE Mold under the microscope - photo identification of the most common indoor molds found in buildings
Mold FAQs Answers to Most Questions about Indoor Mold, Mold Related Illness, Mold Cleanup, Mold Prevention
US EPA: Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab or to any mold lab you wish
Most Common Indoor Molds Found in buildings, A Table of
Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold

Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.

Fiberglass building insulation and HVAC duct work insulation hazards
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Other environmental risks: Asbestos, carbon monoxide, electromagnetic fields, environmental illness, fiberglass, MCS - multiple chemical sensitivity, toxic gases, etc
Indoor Gas Sampling Plan for Residential buildings lists a number of toxic indoor gases which we test for, depending on the building complaint and building conditions
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings, and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some help from a licensed pest control expert.


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