InspectAPedia ^®

This document explains a very common mistake in mold cleanup jobs: relying on bleach, biocides, or fungicides to "kill" toxic mold. This is a chapter of the Mold Action Guide, 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 article series 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 FUNGICIDAL SPRAY & SEALANT USE GUIDE, see BLEACHING MOLD, Advice about and step by step mold cleanup advice at MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD and also MOLD CLEANING MISTAKES. See Crawl Space Dryout Procedures if your building is built over a crawl area.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links 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.

HOW TO KILL MOLD: Should We be Trying to Kill Mold?

Many readers have contacted us to ask about using bleach, fungicides, or biocides as a "mold remediation" step and many mold remediation projects we've seen have placed too much reliance on attempts to spray or gas mold to try to "kill the mold and render it harmless" that we've added this brief article on what's "right" and "wrong" about relying on any spray, gas, chemical, or "treatment" to treat problem mold in buildings.

Spraying, Bleaching, or Killing Mold Does Not Kill All of the Spores

First of all, after spraying or gassing "toxic mold" or "black mold" in a building, the bad truth is that the mold is not dead - at least not all of it. Even if you spray bleach all over your "black toxic mold" you won't kill every single spore. I've examined bleached mold samples in the lab. I can usually tease out viable spores from the supposedly "dead" mold sample. To kill every single mold spore using bleach, for example, you'd have to use such a high concentration of disinfectant and you'd have to keep it on the surface for so long that more likely you'd damage the structure - and still miss some toxic spores.

This is particularly true when people rely on spraying rather than physically cleaning or removing moldy surfaces or materials.

To be scrupulously fair, if we sprayed a surface with sufficient force as to actually physically clean it (and if we removed all of the sprayed-on liquid and debris, we'd do a credible job of cleaning the surface of problem mold. Of course in fact, you could use water or deck cleaner or a dry product like baking soda for such purposes just as well as a disinfectant. See our Report on Media Blasting for an example of using a "spray" approach to physically clean a surface.

- Thanks to Arlene Puentes for technical edits.

Killing Mold Spores Leaves Toxic or Allergenic Particles in Place

Second - even if in theory we could "kill" every spore, the assumption that they are unimportant is highly questionable. "Dead" spores often contain allergens or toxins that are just as harmful to someone breathing them or getting such mold in one's eye or in a cut, as before.

Relying on Mold Sprays, Bleach, Biocides, Fungicides Risks Taking an Ineffective "Short Cut" to Mold Removal

Third - when I hear remediators or testers focused on whether mold is "alive" or "dead" I am immediately concerned that they do not understand the best practices regarding mold problem diagnosis and cure.

The object is not to "kill" mold, it is - to remove the mold reservoir in the building by physical cleaning or in cases of items that can't be cleaned, such as drywall, soft goods, carpets, furniture, or insulation, remove the moldy material - to identify the cause and make sure that's been corrected (which in your case you think has been done but I'm doubtful where a crawl space is involved - wet conditions that made part of a building wet have often affected other building areas that are less obvious).

It is Important to Find, Identify, and Remove All of the Problem Mold Reservoirs in a Building

Fourth and very important - we need to be very confident that ALL of the substantial mold reservoirs at a building have been identified and cleaned-up or removed.

My experience is that very often people focus too quickly on the mold that they see, say on wood in a crawl space, and fail to detect an as large or larger and as problematic or more harmful mold reservoir that they didn't "see". Examples of this mold killer approach error include:

• Missing hard to see but important mold contamination: Failure to recognize that other materials exposed to moisture or leaks, such as insulation, have become a mold reservoir, because to the eye the look "clean"
• Failure to identify all of the mold reservoirs in the building
• Mistaking the visible mold for the most problematic mold - a simple identification test of the visible mold may, for example, show that it is a different genera/species from mold showing up in settled-dust tests or air tests in the same building. If that occurs, further investigation is needed.

Hire a Competent Professional for a Thorough Visual Inspection for Problem Mold and Its Causes

SO what you need (and might already have) is great confidence that the expertise of the mold or building inspector and the scope of the investigation have been very accurate and thorough before any remediation project is begun. Otherwise the risk is that you have to repeat the process again later.

Even if you clean or remove problem mold thoroughly, if you do not correct the original cause of mold growth, you are likely to face this trouble and cost all over again.

How Should Small Areas of Mold be Handled?

Small Areas of mold: clean and disinfect surfaces: small areas of mold (less than 10 sq.ft. or less than 30 sq.ft. in some guidelines)can be cleaned by most property owners using common household cleaners or simple soap and water; if using bleach, extra caution is in order.

While demolition/removal of building components in of small areas of mold may not be required, in some cases removal/replacement of moldy materials permits valuable additional investigation for hidden mold, and may be easier than cleanup, particularly where surfaces or materials are in poor condition or where mold is on drywall or other components such as fiberglass insulation or duct work which can't be cleaned. If further investigation, renovation or repair discloses mold or conditions which cause growth of large areas of mold, professional cleanup/removal by an expert remediator would be needed.

How Should Large Areas of Toxic or Allergenic Mold be Handled?

Large areas of mold (more than 30 sq.ft. of contiguous problem mold): professional cleanup is needed by an expert remediator and is likely to involve significant expense. "Large" is more than 10 sq.ft. according to the US EPA, or 30 sq.ft. per the NY City Guidelines. For instructions for remediation see the NY City guidelines at http://InspectAPedia.com/sickhouse.htm#action. If your remediator is not familiar with these guidelines s/he may not be properly informed to do the job

Share this Article      

...

Technical Reviewers & References

Search InspectAPedia

• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• 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.
• Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com

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.

THE MOLD ACTION GUIDE
MOLD DOCTOR NEEDED?
MOLD EXPERT, WHEN TO HIRE
DO IT YOURSELF MOLD CLEANUP
HOW TO FIND MOLD
MOLD CLEANUP GUIDE
MOLD KILLING GUIDE
MOLD REMEDIATION CLEARANCE INSPECTION
ACCEPTABLE MOLD LEVEL
AFTER THE MOLD CLEANUP
MOLD PREVENTION GUIDE
OTHER IAQ ISSUES

Detailed Procedures for the Clean Up or Removal of Toxic or Allergenic Mold in Buildings

Mold Cleaning Procedures & Mold Remediation Standards Guidelines

• BLEACHING MOLD, Advice about - guide for using bleach, when and how and why and why not to use bleach on mold
• 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
list of links to documents including other States: California Mold Cleanup Standards, Texas Mold Cleanup Standards, Pennsylvania Mold Cleanup Standards, EPA, CDC, and other U.S. state, federal, and world mold standards
• 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
• ...

More Information on Building Diagnostic Inspections and Repairs

...

InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.

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

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting

Contact Daniel Friedman for website content suggestions or for fee-paid consulting