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Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
MOLD: A COMPLETE GUIDE to TEST CLEAN PREVENT
ACCURACY vs PRECISION of MEASUREMENTS
ACTIVITY of MOLD in buildings
AGE of MOLD - Old is the Mold?
AIR POLLUTANTS, COMMON INDOOR
AIR TEST SAMPLING CASSETTE STUDY
AIRBORNE MOLD COUNT NUMBER GUIDE
AIRBORNE PARTICLE ANALYSIS METHODS
ALLERGEN TESTS for BUILDINGS
ALLERGENS in BUILDINGS, RECOGNIZING
ALLERGY & MOLD IAQ PRODUCTS
ALLERGY TESTS for PEOPLE
ALLERGY TEST ACCURACY
BASEMENT MOLD WATER IMPACT
BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ
BIOLOGICAL POLLUTANTS in the HOME - EPA
BLACK MOLD, HARMLESS COSMETIC
BLACK MOLD, TOXIC & ALLERGENIC
BLEACHING MOLD, Advice about
BOOK MOLD, Moldy Book Cleaning
BOOKSTORE - ENVIRONMENTAL
CAR MOLD CONTAMINATION
CARPET DUST IDENTIFICATION
CARPETING & INDOOR AIR QUALITY
CARPETS & PADDING ODORS IN buildings
CHINESE DRYWALL HAZARDS
CLEARANCE INSPECTIONS - MOLD CLEANUP
DIRECTORY of MOLD / ENVIRONMENTAL EXPERTS
DIRT FLOOR MOLD CONTAMINATION
DISINFECTANTS & SANITIZERS, SOURCES
DISINFECTING BUILDINGS with BLEACH
DO-IT-YOURSELF MOLD CLEANUP WARNINGS
DRYWALL MOLD TESTING
DUCT SYSTEM & DUCT DEFECTS
DUST, HVAC CONTAMINATION STUDY
EFFLORESCENCE, Salts & White / Brown Deposits
EMERGENCY RESPONSE, IAQ, GAS, MOLD
FEAR of MOLD - MYCOPHOBIA
Fiberboard Insulation Sheathing Mold
FIBERGLASS INSULATION MOLD
FIND MOLD, ESSENTIAL STEPS
MOLD in BUILDINGS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOODS IN buildings-mold
FLOOR & SUBFLOOR MOLD, HIDDEN
HIDDEN MOLD, HOW TO FIND
HUMIDITY CONTROL & TARGETS INDOORS
INDOOR AIR HAZARDS TABLE
Indoor Air Pollution Book Online CPSC
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
INDOOR AIR QUALITY METHODS COMPARED
LAB PROCEDURES MICROSCOPE TECHNIQUES
Legionella BACTERIA & HVAC Equipment
MEDIA BLASTING for MOLD REMOVAL
MILDEW in BUILDINGS ?
MILDEW ERRORS, IT's MOLD
MILDEW REMOVAL & PREVENTION
MOISTURE CONTROL in BUILDINGS
MOLD: A COMPLETE GUIDE TO MOLD
MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD
MOLD COUNT NUMBER GUIDE
MOLD CULTURE TEST KIT VALIDITY
MOLD DETECTION & INSPECTION GUIDE
MOLD or INDOOR AIR EMERGENCY RESPONSE
MOLD LEVEL IN AIR, VALIDITY
MOLD ODORS, MUSTY SMELLS
MOLD PREVENTION GUIDE
MOLD RELATED ILLNESS GUIDE
MOLD SAFETY WARNINGS
MOLD TEST KITS
MOLD TESTING METHOD VALIDITY
MSDS Material Safety Data Sheets
MYCOPHOBIA, STAINS MISTAKEN for MOLD
ODORS GASES SMELLS, DIAGNOSIS & CURE
OZONE for MOLD OR ODORS
PAINTS & COATINGS ODORS IN BUILDINGS
PARTICLE SIZES & IAQ
Particulates & Allergens Indoors
RADON HAZARD TESTS & MITIGATION
RENTERS & TENANTS GUIDE TO INDOOR HAZARDS
SMELL PATCH TEST to Track Down Odors
SEWAGE BACKUP TEST & CLEANUP
STAINS on & in BUILDINGS, CAUSES & CURES
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
STAINS & Thermal Tracking
THERMAL IMAGING MOLD SCANS
THERMAL TRACKING & THERMAL BRIDGING
TRAPPED MOLD BETWEEN WOOD SURFACES
TRAPPED MOLD BETWEEN WOOD SURFACES
UV LIGHT BLACK LIGHT USES
VOCs VOLATILE ORGANIC COMPOUNDS
Bleach to kill mold? This article explains the usual bleach solution used to clean or disinfect building surfaces and we describe how to use bleach to clean a moldy building surface. We explain when the standard bleach solution cleaning method is useful as well as when it's probably a big mistake.
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GUIDE TO USING BLEACH - Bleach as a "Mold Medicine" to try to kill mold or prevent mold in buildings
Readers should also see MOLD SPRAYS, SEALANTS, PAINTS for a discussion of other mold killing chemicals and encapsulants.
[Click to enlarge any image]
Our photo at page top shows a moldy home after flooding in Jasper Texas. The drywall and other soft materials needed to be removed, not "sprayed with bleach". But after all demolition and loose debris cleaning, use of a biocide as a final wash is common in this circumstance.
What about a small patch of mold on a bathroom wall or ceiling? This article explains the use of bleach on moldy surfaces.
Bleach, diluted bleach, or bleach sprays used in cleaning may be appealing but they are unnecessary, potentially dangerous (if you get bleach in your eyes), and the use of bleach tends to lead to improper and inadequate cleaning - if you substitute "spraying bleach" for actually cleaning or removing the mold your cleanup will not be successful.
Our photo (left) shows hard surfaced wall paneling and floor tiles that might be cleaned of light mold contamination using a household cleaner or a dilute bleach solution (described below). But before cleaning mold off of this wall we'd want to know about the wall cavity - if there have been leaks into the wall cavity itself, cleaning the surface alone is probably futile.
The object of mold removal is to clean the surface, to remove loose moldy material, not to try to sterilize the surface. The object of mold remediation is to clean, or remove, the majority of the mold particles (spores, conidiophores, hyphae, mycelia) from the target 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.
The operative word to fix in mind is to "clean" or "remove" the problem mold. "Killing" the mold is not the object - first of all because our lab work shows that you're unlikely to kill all of the mold on a surface using bleach, unless you use it at a concentration and duration which is so strong that you're likely to completely destroy the "bleached" material, and second of all because even if you could "kill" every mold spore, you are at risk of leaving toxic or allergenic particles in place - they may be dead but still toxic. See MOLD KILLING GUIDE for details.
"Mold removal" by surface scrubbing only works if you're cleaning a relatively hard, non-porous surface such as finished wood, painted metal, or plastic. Soft materials like Sheetrock™ or drywall which have become moldy generally should be removed, the exposed surfaces cleaned, and then new drywall can be installed (after you've also corrected the reason for the mold growth in the first place).
Just spraying or painting-over mold with anything if spraying of fungicides or sealants is to be used in place of actual cleaning or removal of mold is an improper and inadequate practice which risks leaving a reservoir of toxic or allergenic particles in the building.
Guide for Using Bleach to Clean a Building Surface
If you want to use bleach as a cleaning agent instead of other cleaners (household cleaners, or plain soap and water would work just fine for cleaning a moldy surface) here are some mold cleanup suggestions for homeowners from the Canadian Mortgage and Housing Corporation CMHC.
Keep in mind that bleach is a powerful oxidant that is not only dangerous on skin or in eyes, but it will also bleach (whiten) the surface where you're using it, or your clothes or whatever is around if you're sloppy.
Using Bleach as a Water Disinfectant or to Shock a Well
More Information about disinfectants & contamination cleanup procedures
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs) about using bleach as a household cleaner, for mold cleanup, in wells as a water disinfectant, etc.
Question: I heard that using bleach straight will encapsulate the bacteria or virus
Dear friends, first of all I love your web site. It must have been a real labor of love to build. Good job. I was told a while back that one must dilute household bleach for it to disinfect a surface. I heard that by using it straight it will encapsulate the bacteria/virus’ you are trying to clean. Would you know if this is true? Thank you very much for your time. B.S., Sparrow Bush NY
Reply: Nonsense. There are different reasons for diluting bleach but not the one you offer. But indeed some encapsulated pathogens such as Staphylococcus aureus are resistant to bleach disinfectants, diluted or in higher concentrations.
Bleach (hypochlorite) has been used as an effective disinfectant for more than 100 years  and interestingly some "environmentally safe" and "home remedies" used as alternatives are not government controlled and may be significantly less effective. (Ammonia, borax, baking soda, vinegar and one commercial antimicrobial spray product were evaluated.) .
We can find absolutely no basis for the claim that undiluted household bleach "encapsulates" and thus fails to treat bacteria or viral contaminants when used "full strength" as a cleaner, but there is a different reason that household bleach (laundry bleach) is diluted before use: out of the bottle, household bleach is strong enough to damage many surfaces and materials (as well as your eyes and skin) and used full strength it is also a bit difficult to rinse clean. That's the reason that for typical household cleaning uses bleach is diluted 1 part bleach to 4 parts water.
The term "encapsulation of bacteria" is, however, a real one and has been discussed among microbiologists in explaining why it is difficult to treat these pathogens in certain circumstances - but not household cleaning.  That may be where some confusion has arisen.
Bleach as an oxidizing biocide, at normal household cleaning dilutions, is common, widely used, safe, and effective against many pathogens.
It is the case, however, that some pathogens such as Staphylococcus aureusare are indeed resistant to simple bleach as a disinfectant. Diluting or not-diluting the bleach is not pertinent to that problem nor its solution.
Questions & answers or comments about using bleach to "kill mold" or as a building surface cleaner or disinfectant.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Allergies, Allergens, Allergy Testing in buildings - References & Products
Mold Contamination Testing, Cleanup, Prevention: references & products
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.