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This article discusses the use of sprays to address bacterial and mold hazards in buildings. We illustrate when the use of disinfectant or biocidal sprays, fungicides, bleach, paints, and encapsulant coatings are useful, and when they are a mistake. 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.

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When Is it Good Practice to Use Biocides or Fungal sprays in a Building to Address Bacteria or Mold?

Some experts also warn that at least some biocides may be irritating or harmful to building occupants, may leave harmful particles, are only temporarily and only partly effective, and may add moisture that adds problems to the building to the question “When should I use biocides during fungal remediation in buildings?” , the short answer is that use of biocides should be avoided if you can. We agree with the following opinion expressed by Dr. Harriet Burge, our favorite teacher and a respected expert in the field of public health:

Biocides, as the word indicates, are designed to kill living organisms. The simplest answer to the question, is to use biocides when you want to kill something. Answers are never so simplistic, however. Before using a biocide, you should consider the following questions:

1. Is killing the organism going to make a difference in the remediation outcome? The answer to the first question, at least with respect to fungal growth in buildings, is usually “no”. Most illnesses and symptoms related to fungal exposure will occur whether or not the fungus is alive or dead. Also, the use of biocides will only marginally change the speed with which re-growth occurs if suitable moisture conditions recur. Cases where biocides may affect outcomes are in hospitals where infection of immunocompromised patients is of concern, in cleaning up bird droppings infested with Cryptococcus neoformans, or as a delay tactic in areas prone to repeated wetting. Fixing the water problem, or using materials that do not support fungal growth, are better long-term solutions. See MOLD KILLING GUIDE for more about "killing" mold.
2. Is the biocide effective against the organisms of concern in this case? The second question is equally important, especially for fungi. Most biocides were designed to kill infectious bacteria in hospitals and other high-risk environments. Many biocides that work well against bacteria are essentially useless for the control of fungi. Thus, fungi are highly resistant to ozone, ultraviolet radiation, quarternary ammonium compounds, and many other commonly used biocides. Some of these biocides (e.g., ozone) will inactivate some spores in a population and enhance germination for those remaining. For this reason, reliance on biocides is not recommended for the control of most fungi. Examples of biocides that are effective against fungi are: ethylene oxide (useful as a fumigant for wet, moldy books), formaldehyde in high concentrations, and glutaraldehyde in high concentrations. None of these are recommended for use except under exceptional circumstances due to their potential toxicity.
3. Is exposure to the biocide more or less dangerous than exposure to the living agent(s) of concern? For any biocide, it is important to weigh the risks of human exposure to the biocide against the potential benefit of reducing human exposure to the fungal species targeted. For many infectious disease agents for which most biocides were designed, the disease is far worse than exposure to the biocide. So the answer is, for nonspecific building-related symptoms, the risk tradeoff is not so clear-cut.

If possible, biocide use should be avoided. If there is a logical reason to use biocides in a specific case, then care must be taken to insure that the biocide will be effective and that human exposure to the biocide will be minimized. -- Dr. Harriet Burge EM Lab by email 8/30/04

Also see MOLD CLEANING MISTAKES for a master list of the principal ways that people foul up mold cleanup projects.

When is it Good Practice to use Mold Paints, Fungicidal Sealants and Encapsulant Sprays in a Crawl Space or in Other Building Areas?

Once the building has been cleaned of debris and moldy materials, and building leaks, moisture traps, or crawl space water has removed, and after we've eliminated the sources of building water entry, we are ready to take the next steps to keep the building clean and dry.

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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.

FUNGICIDAL SPRAY & SEALANT USE GUIDE
BLEACHING MOLD, Advice about
MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD
MOLD CLEANING MISTAKES
Crawl Space Dryout Procedures

• Harriet Burge, Harvard School of Public Health, and EM Laboratory, a private mold and environmental testing lab - email to D.F. August, 2004. Dr. Burge is an educator, writer, and consultant in the field of indoor air quality and mold contamination. The author has studied aerobiology and microscopy in courses taught by Dr. Burge.
• Product literature and MSDS sheets for the biocides and fungicidal sealants listed in this article.
• US Centers for Disease Control, CDC: www.cdc.gov/ncidod/diseases/hanta/hps/ describes the risks associated with hantavirus.

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