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Remediation of Environmental Moulds(Cleaning Up the Mould)
Remediation (cleanup) covers a broad range of topics. Several good references are available [90, 93, 95, 98], and we summarize some of our favorites on our resources page. Before reading further, please also remember that you will never be able to eliminate all traces of a fungus from your environment. Fungi are present in all indoor environments ! Indeed, fungi are very important to the world's ecology!
For remediation to be successful, the following issues must be considered carefully:
Why Did the Infestation Occur?
Fungi require food and water. The building or its contents serve as the food, and it is the water intrusion (entry) that permits fungal overgrowth. Any remediation process is ultimately doomed to failure if the cause(s) of local water accumulation are not addressed. If water remains, the fungi will return!
Where is the Infestation?
As we discuss in detail elsewhere, looking for fungi mainly proceeds with the senses of smell and sight. But, the added step is that you must always consider the possibility that the fungus extends beyond what you see. If not removed, hidden mould contamination can definitely come back to haunt you.
Involved materials come in three broad categories. Truly porous materials (wall board, ceiling tiles) will have fungus that has deeply penetrated their surface. These must be discarded. Semi-porous materials (concrete, wood) may have varying levels of fungal penetration. These can often (but not always) be cleaned. Non-porous surfaces (plastics, ceramics) usually have only surface contamination and an usually be readily cleaned.
Ceiling tiles and wall board (sheetrock) are often the trickiest. You need to be sure to see both the front and the back of surface! Vinyl wallpaper is notorious for trapping moisture underneath itself and thus promoting fungal growth. Fungi are well known for growing inside walls and on the top of ceiling tiles!
Decide on a Remediation Plan
Once you have control over moisture, you then decide how to clean up the problem. Small areas of infestation can often be cleaned up with simple tools, and we offer a step-by-step approach below. Larger areas, however, should usually be tackled by a professional cleanup firm. The more extensive the contamination, the greater the personal risk of exposure during the cleanup process. Extensive containment procedures maybe required to prevent damage to other parts of the building. The EPA document entitled Mold Remediation in Schools and Commercial Buildings gives a great deal of insight into the potential level of complexity of a large cleanup process.
As a particular point area of current interest, the CDC has released a document that addresses the question of flood-damaged homes.
Your remediation plan should also include a monitoring plan. How are you going to decide if you have removed all the moisture? Generally, one needs to reduce the moisture content of porous materials such as wallboard to < 15%, and this can be monitored with a variety of hand-held moisture meters. How are you going to measure humidity in the environment? The target here is 30-60% relative humidity (30-50% is better) and again, a variety of hand-held meters are available. Don't rely on just one set of readings! Things change with seasons and operation of the heating vs. the cooling aspects of the HVAC system. If you had moisture problems once, they may recur. Systematic surveillance may be needed!
This is a very important point! That dry, fuzzy clump of fungus is often covered with tiny spores that are designed by nature to be spread through the air. If you disturb the dry fungus, you may easily produce a tremendous cloud of fungi that will spread throughout your home or building. There are three specific points to be made in this regard:
Get It Wet Before You Clean It Up
While moisture is the cause of your mould problem, you paradoxically need to carefully add moisture (without splashing!) during the cleanup process. If you are about to remove a large amount of fuzzy fungus, get it wet first! This can be done by wetting the surface gently with either water or disinfectant. This will reduce the number of spores that are spread throughout the environment.
Mould-Infected HVAC (Heating, Ventilation, Air Condition) Systems
If you suspect that an out-of-service HVAC is contaminated with moulds, don't turn it on! Doing so could blow the fungus throughout the building.
Usually, the amount of fungus on the top of the ceiling tile will be much greater than what you can see on the bottom. You need to get BOTH sides wet before you remove the tile. Approach the contaminated tile by first removing an adjacent UN-contaminated tile. Be sure to discard the tiles in a plastic bag that can be tightly sealed.
- Wear gloves! You should also wear a good quality mask. For best protection, ask at the hardware store for a mask that is rated N95 or better.
- Dried moulds are easily scattered about the house whereas wet moulds are sticky and will stay put. Thus, during the actual cleanup phase it is best if the surface of the mouldy material is wet. This may mean that, paradoxically, you are going to re-moisten at least the surface of the material with water or disinfectant. The fungal spores that may be on the surface of the contaminated material will be spread less easily if they are dampened before being wiped away.
- Involved materials come in three broad categories. Truly porous materials (sheetrock, ceiling tiles) will have fungus that has deeply penetrated their surface. These must be discarded. Cloth-covered furniture can sometimes be cleaned by using a very high efficiency vacuum process (referred to as HEPA vacuuming), but this is expensive and simply discarding the furniture may make the most sense. Semi-porous materials (concrete, wood) may have varying levels of fungal penetration. These can sometimes (but not always) be cleaned. Non-porous surfaces (plastics) usually have only surface contamination and are readily cleaned.
- Bag and discard grossly infested materials such as sheetrock. It is best if the surfaces are at least damp during this process, as this will reduce the spreading of the spores. Carpet is a special problem, and thorough cleaning may be impossible. Discarding it may well be the easiest solution. Be sure to remove all of the contaminated material plus (if applicable) a rim of unaffected material. With sheetrock for example, it is often suggested that one remove a 12" rim of clean unaffected material beyond the area of obvious damage.
- Allow the area to dry.
- Clean the surface with a standard detergent. (See below for discussion of use of cleaning agents stronger than detergent.)
- That should do it! Your surface(s) should now be clean, dry, and free of mould. Depending on your setting, you may choose to retest the surface to verify that the remediation was done properly. Remember that keeping surfaces free of mould is a function of preventing moisture from accumulating.
Old Guidance on Using Bleach for Cleanup
Cleaning with detergent will only remove fungus by mechanical means -- simple detergents generally can't kill the fungal spores. Prior guidance from the EPA has suggested use of bleach as a final disinfection step. However, this procedure can be hazardous and current guidance omits this step. We are including our old notes on the process here so that the information and its hazards are available. But, the process is not recommended any longer. If you having something that you believe requires this degree of disinfection, consultation with a professional is advised.
- TO USE THESE STEPS, YOU MUST NOT USE AN AMMONIA-CONTAINING CLEANER (DETERGENT). MIXING AMMONIA WITH BLEACH CAN CAUSE RELEASE OF VERY TOXIC GASES CALLED CHLORAMINES. THESE GASES CAN CAUSE COUGHING, A FEELING OF SUFFUOCATION, OR EVEN DEATH!
- After cleaning with the detergent, thoroughly rinse the surface.
- BE SURE YOUR WORK AREA IS WELL VENTILATED!
- Disinfect the surface with a 10% solution of bleach. That is, mix ~1.5 cups of bleach with each gallon of water. Thoroughly swab the infected surface. Remember, no ammonia-based detergents are allowed at any step in this procedure. Also, be sure your work area is well ventilated. Bleach fumes are irritating to the nose, throat, and eyes. Bleach can also damage your clothes or shoes.
- Allow the bleach solution to dry in place. Do not rinse it off. It is during this step that the fungal spores are actually being killed.
You are done with cleanup with (a) there is no visible mould, (b) there are no mould odors, and (c) you have fixed the moisture/water problem so that it will not recur .
Repeat after me: Moisture makes fungi grow, moisture makes fungi grow, moisture makes fungi grow! This mantra is absolutely the key. But, sometimes it is hard to know why the moisture is appearing. Short of a leaking pipe, moisture generally appears due to condensation on surfaces that are at or below the dew point for a given relative humidity. For example, an exposed outside corner of a building might be just cool enough to cause condensation of moisture that doesn't occur on adjacent walls. Or, the cool air flowing out of an air supply vent might hit a section of wall such that the wall cools enough to condense moisture. For more on this topic, see the Moisture, Mold, and Mildew discussion in Appendix C of the EPA's Building Air Quality: A Guide for Building Owners and Facility Managers.
As a supplemental step, you might consider making the surface fungus-resistant. Many building materials with anti-fungal properties are available. For example, you might choose to replace moisture-prone carpeting with an indoor-outdoor carpet that is fungus resistant. Paints that contain antifungal compounds are available (see, for example the paint called Portersept® on the Porter Paints website. Likewise, caulking compounds that incorporate antifungal compounds are also available (see, for example, the product called DAP Kwik Seal Plus.)
We are very often asked about whether one must discard clothing or other household goods that have either been exposed to a "contaminated environment" or actually had mould growing on them. Objects with non-porous surfaces can usually just be wiped clean. And, as stated so nicely in the American College of Occupational and Environmental Medicine's position statement , "Colonized porous materials, e.g., clothing or upholstery, can be cleaned using appropriate routine methods, e.g., washing or dry cleaning clothing, and need not be discarded unless cleaning fails to restore an acceptable appearance."
Remediation of water-damaged papers is discussed only by the EPA . For non-valuable items, they recommend discarding the materials. For important papers, they recommend that one photocopy the items and then discard the originals. As a temporary measure, one can freeze (in frost-free freezer or meat locker) or freeze-dry the papers. Similar principles apply to to books and photographs. The American Institute of Conservation website provides a number of useful tips and also provides contact information for professional conservators.
Handling of materials that have merely been exposed to high humidity is not discussed anywhere at all. The closest discussion in spirit is a discussion of handling steam-damaged materials that is provided on the University of Minnesota web site. Basically, clean materials are simply dried and monitored. Again and again, we come back to the principal of visual and olfactory assessment for moulds. These concepts are echoed in comments in other documents [90, 95], but specific discussions of this issue are lacking. For example, the EPA Mold Remediation in Schools and Commercial Buildings document  states "Once dried out, clean NON-moldy materials within 48 hours to prevent mold growth." Clearly, dry, NON-moldy materials would appear to already be acceptable for continued use.
We provide specific literature references on most of our pages. However, we also have a separate page devoted just to a critical summary of the mould-related literature that is readily found on the web. Check it out!
About These Pages
The material and ideas here are drawn from many sources, including our own experience. However, this is an area with few guidelines and even fewer hard facts. So, you must always apply common sense in choosing how to adapt the ideas presented here to your own situation.
When in doubt, please consult with a professional. You can find experts in this field by searching on the term "mould remediation" in your favorite search engine. At times, there is simply no substitute for experience and personal knowledge.
82. Anonymous. 2002. Adverse human health effects associated with molds in the indoor environment. American College of Occupational and Environmental Medicine (www.acoem.org), Arlington Heights,IL.
90. Anonymous. November 2000. Guidelines on Assessment and Remediation of Fungi in Indoor Environments. New York City Department of Health, Bureau of Environmental & Occupational Disease Epidemiology (www.ci.nyc.ny.us/html/doh/html/epi/moldrpt1.phpl), New York City, NY.
93. Anonymous. March 1998. Indoor Air Quality Info Sheet. Indoor Air Quality Section, Calirfornia Department of Health Services (http://www.cal-iaq.org/mold9803.php), Berkeley, CA.
95. Anonymous. March 2001. Mold Remediation in Schools and Commercial Buildings, EPA 402-K-01-001. United States Environmental Protection Agency (www.epa.gov/iaq), Washington, DC.
98. Anonymous. October 1997. Should you have the air ducts in your home cleaned? EPA 402-K-97-002. United States Environmental Protection Agency (www.epa.gov/iaq), Washington, DC.
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