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Flooded House Cleanup
- 1. Flooded House Clean-up Kenneth Hellevang, Ph.D., P.E.
- 4. Flood Sights
- 5. Flood Sights
- 6. Inspections
- 13. Mold Occurs within 2 to 3 days
- 15. Mold Test Kits Test Results are Not Accurate!
- 18. Mold Hazard Air moves from stud wall cavity into living space
- 28. Grand Forks 1997
- 30. Minot Guidelines
- 33. HVAC
- 48. Measure Humidity ½ cup water ¼ cup salt 75% RH @ 12 hrs.
- 51. Moisture Meters
- 54. Mold or Salt
- 55. Search for NDSU Flood Information http://www.ag.ndsu.edu/flood
Editor's Notes
- Air cleaners and other units do not compensate for a poor job of flood recovery. Air filters remove only some of the mold spores floating in the air. Mold spores will settle on furniture and other surfaces and not be removed by air filters. Air filters do not remove all the mold particle proteins that people may be allergic to and do not remove the volatile organic compounds released by mold. Units that produce ozone do not kill mold or other biological materials in the air. The ozone concentration required to have some effect on mold or other materials is far greater than produced by the units and exceeds concentrations that are safe for occupied areas. Ozone is a lung irritant. Units that produce ozone are not effective and should not be used in occupied spaces. Units that produce hydroxyls are similar to ozone in that hydroxyl is an oxidizing agent for odor control. Hydroxyl may be effective for killing mold under very controlled concentration and exposure conditions. However, what is important is will the unit be effective in a uncontrolled environment. Also, remember that killing mold does not eliminate the potential health effects. Ultraviolet light may be effective under controlled concentration and exposure conditions, but is typically not effective in removing mold or other contaminants in an infested environment. Again, air cleaners and other units do not compensate for a poor job of flood recovery. Remove the flood damaged or mold infested materials to create a healthy living environment.
- The Institute of Inspection, Cleaning, and Restoration Certification provides guidance on water damage restoration.
- IICRC provides recommendations based on the source or type of water causing the damage. Basement seepage would be clean water and designated as category 1. Water from sump pumps and other locations that contains some contamination and microorganisms is designated as category 2. Water that contains sewage and chemicals is designated as category 3. Surface flooding is listed in category 3 because it is unknown what is in the water.
- Mold will develop within 2 to 3 days, so materials need to be rapidly cleaned and dried. Frequently mold growth will occur in hidden locations such as within wall cavities and behind wall coverings.
- Scientific evidence links mold and other factors related to damp conditions in homes and buildings to asthma symptoms in some people with the chronic disorder, as well as to coughing, wheezing, and upper respiratory tract symptoms in otherwise healthy people, says a report from the Institute of Medicine of the National Academies in 2004. An uncommon ailment known as hypersensitivity pneumonitis also is associated with indoor mold exposure in genetically susceptible people. Damp conditions and all they entail may be associated with the onset of asthma, as well as shortness of breath and lower respiratory illness in otherwise healthy children, although the evidence is less certain in these circumstances. Likewise, the presence of visible mold indoors may be linked to lower respiratory tract illness in children, but the evidence is not as strong in this case. The study was sponsored by the Centers for Disease Control and Prevention. The Institute of Medicine is a private, nonprofit institution that provides health policy advice under a congressional charter granted to the National Academy of Sciences.
- Mold test kits that are purchased from hardware stores or off the internet will not provide accurate useful information.
- A common test kit includes a petri dish that is exposed for a period of time, then allowed to grow. Since there are always mold spores in the air, there will always be some mold growth. This may cause undue concern about a contaminated environment when there is only a normal amount of mold spores in the air. Typically the dish must be shipped to a laboratory for interpretation. Their report will indicate the types of mold growth and a quantity value, but can not determine if you do or do not have a mold problem.
- People react to mold whether it is living or dead. It must be removed! It cannot just be killed with a biocide. People still can have health effects from mold exposure even though it has been killed with bleach or other biocide. Porous materials are those that will absorb water such as ceiling tiles, carpeting, upholstered furniture and wall board. They must be discarded if they are moldy. It is impossible to adequately remove mold from these materials. Mold can be removed from non-porous surfaces such as metal, concrete and hard plastic. If there is extensive mold growth, the surface should be vacuumed using a HEPA filter to minimize the amount of mold particles released into the air during cleaning. Wash with a detergent solution. After the surface is clean, it can be sanitized using a biocide, but since the mold has been removed by washing the surface, recommendations from some organizations do not include using a biocide. The surface needs to be thoroughly dried after it is cleaned to prevent future mold growth. Semi-porous materials, such as structural lumber, can generally be saved by removing the mold. Frequently mold growth is limited to the surface, so it can be removed by scrubbing with a brush or other vigorous cleaning. To minimize future mold growth, a biocide is used to kill any mold that was not removed during cleaning. Make sure that the wood is rapidly dried.
- Air moves from a wall cavity into the living space through openings such as electrical outlets. Therefore, people will be affected by mold within the wall cavity. It is very important that walls be opened to quickly and adequately dry to prevent mold growth. Mold on the oriented strand board needs to be removed or it may affect people living in the house. Usually the mold is just on the surface and can be removed with scrubbing or light sanding with dust collection. Treating it with a biocide or covering it with some type of sealer is not adequate!
- Provide respiratory protection when working in moldy or bacteria contaminated areas. At a minimum wear a mask that has an N-95 or better rating. These masks will have two straps rather than one. Make sure that the mask fits properly to filter the air you breathe. Breathing through a mask requires more effort, so pace yourself as you work.
- Use eye protection when working with chemicals and for general eye protection.
- Discard carpet that has been saturated with category 3 water. Category 2 water contamination may be cleaned with hot water extraction and biocide. This typically is done by a professional carpet cleaner. If water reached subflooring, the floor covering should be removed and the subflooring cleaned, disinfected and dried. Saturated subflooring needs to be exposed for it to dry.
- Porous materials exposed to flood waters should be discarded, since it is impossible to adquately clean them. Some materials included in this category are carpet pad or cushion, absorbent stuffed fabrics such as in furniture, ceiling tile, dry wall (sheetrock), and paper. Depending on the type and level of contamination, clothing may be laundered. Evaluate structural materials such as studs and floor joists for degree of contamination. Consult professionals if fuel oil or chemicals have been involved.
- Remove water from the basement slowly. If your basement is full or nearly full of water, pump out just 2 or 3 feet of water each day. If you drain the basement too quickly, the pressure outside the walls will be greater than the pressure inside, causing the walls and floor to crack and collapse
- During mold removal, the area needs to be isolated to prevent mold spores and particles from entering the remainder of the house and causing contamination that needs to be cleaned. Containment should include isolating the heating and air conditioning systems to prevent debris from contaminating the ducts and unit. Enclose the work area with polyethylene, place the work area in negative pressure by using a fan blowing air to the outdoors from the work area, and protect the rest of the contents by removing them the work area.
- Heating, ventilation and air conditioning, HVAC, systems need to be thoroughly cleaned, reconditioned, or replaced if they were submerged in flood water. A professional technician should evaluate the condition of the HVAC system. Frequently it is easier to replace the ducting than to adequately clean it. Use only products specifically approved for use in human housing air handling equipment.
- Water will typically permeate into the wood below a vinyl or ceramic floor, so the floor covering should be removed to ensure that the wood adequately dries. Moisture content should be measured with a meter.
- All electrical fixtures (switches, outlets, breakers, wire) submerged in flood water need to be replaced. Electric motors need to be professionally reconditioned or replaced. Contact an electrician or electrical inspector for advice.
- Flooded crawl spaces need to be ventilated to dry. Place a fan blowing to the outdoors and provide several air inlets to assure the crawl space is adequately ventilated. Remove existing plastic to permit airflow over the wet soil and materials. After the soil is dry, place a 6-mil plastic on the soil and seal it to the walls.
- Shovel out wet mud, then flush non-porous materials with water to remove mud and other deposits. Scrub the surface using detergent starting at the bottom. After the surface is clean, it may be disinfected using a biocide such as a chlorine bleach and water solution.
- Biocides are products that kill biological material and must be used according to the product label. Many biocides are for specific types of materials, such as nonporous materials, and specific applications. If a specific use is not included on the label, it should not be used for that application. For example, it may be for use on metal but not include use for heating, ventilation, and air conditioning systems. Biocides kill biological material that exists at the time of treatment but do not provide control in the future. Use the recommended concentration for the biocide to be effective. For example, generally ½ to 1 cup of chlorine bleach is mixed with one gallon of water. To be effective the biocide should be used on a clean surface after it has been cleaned with a detergent. For example, organic material will limit the effectiveness of chlorine bleach. Biocides require exposure for a period of time to be effective. For example, a surface treated with a bleach water solution should remain moist for about 10 minutes to be effective. Use personal protective equipment such as gloves when using a biocide and ventilate the area. Chlorine bleach may irritate your respiratory system. Chlorine bleach is the most common biocide used for flood clean-up, but other products can be used according to their label. Some bleach does not contain chlorine, so it will not be effective as a biocide. Make sure that the bleach contains sodium hypochlorite.
- All surfaces need to be exposed to dry air for drying to occur. A floor covering, such as the vinyl shown in the picture, should be removed to dry the material under the floor covering. Enclosed areas such as wall cavities need to be opened and exposed to dry.
- Moving air across the surface using fans aids drying Moisture needs to be removed from the house for drying to occur. The best method to remove the moisture is to exchange moist inside air with dry air from outside. Place a fan in a window or door facing to the outdoors. Seal around the fan using some type of sheeting to prevent air recirculating to the suction side of the fan. The fan will create a vacuum within the house that will draw dry outside air into the house through windows or other openings. Ventilation should continue until the structure is dry and indoor air relative humidity remains below about 60 percent.
- Indoor air relative humidity should be kept low to aid drying. It is desirable that the relative humidity should be below about 50 percent if possible. Ventilation should be used whenever possible since it will most efficiently remove large amounts of moisture. When outdoor air relative humidity does not permit ventilation, mechanical dehumidification can be used. Most home dehumidifiers will only remove a few pints of water per day, while ventilation can remove several gallons of water per day. Dehumidifiers will remove more moisture from high humidity environments than low humidity environments and will lower the relative humidity to about 50 percent. Air conditioners also can be used to remove some moisture from the air.
- Monitor the relative humidity in the house using a hygrometer. A hygrometer needs to be calibrated to ensure accuracy. The hygrometer should read about 75% after being placed in a plastic bag with a cup containing about ½ cup of water and 1/4 cup of salt for a period of at least 12 hours. The hygrometer should be calibrated annually, since hygrometers tend to drift. Digital hygrometers will provide a more rapid measurement and may be more accurate.
- Warming the air increases its moisture holding capacity which aids in dehumidification. However, the rate of mold growth also increases at warmer temperatures. Keeping the house at a normal indoor temperature or slightly cooler provides the benefit of warmer temperatures while limiting the growth rate of microorganisms.
- Processed materials such as paper are much more likely to have mold growth than unprocessed material such as structural lumber. Therefore, even though wood decay does not occur until the wood moisture content exceeds about 20%, the wood moisture may create a moist environment in an enclosed wall that will lead to mold growth on the dry wall paper. Mold growth typically occurs at relative humidity levels exceeding about 70%. This corresponds to wood with a moisture content of about 15%. Do not enclose walls until the wood moisture content is less than 15%.
- Wood moisture content should be measured with a meter to assure that the wood moisture is below 15% before rebuilding. Wood moisture meters can be borrowed from most NDSU Extension Service county offices. Require contractors to measure the wood moisture content before enclosing walls or covering subfloors.
- Soils become saturated during flooding. It will take a very long time for the soil to dry. Soil moisture moves through the basement wall in a liquid or vapor form and can introduce gallons of water into the house each day. This moisture needs to be removed to prevent moisture damage to the house and to permit drying. It will take weeks or months for the soil to dry and the moisture flow into the house to stop.
- Moisture will move through a concrete basement floor or wall in vapor form for many weeks until the soil around the basement has dried. One method for determining if moisture is coming through the concrete is to tape a piece of clear plastic about 3 feet by 3 feet in size to the concrete for a period of several days. Any moisture accumulation indicates that moisture is still coming through the concrete. Floor and wall coverings should not be installed until the moisture flow discontinues for several weeks.
- A fluffy white material on a concrete floor or wall is frequently a salt deposit rather than mold. Sodium and magnesium sulfates are found frequently in North Dakota. These salts are dissolved and transported in groundwater readily. As the water comes through the concrete, the water evaporates and leaves the salt on the surface. The deposits often take on a white, fluffy or moldy appearance in cracks in the floor or wall. Since these deposits are dissolved easily by water, putting a few drops of water on the substance is one way to determine if it is salt or mold. Calcium and magnesium carbonates also are found throughout North Dakota, but they are relatively insoluble in water. Upon evaporation, they cause light-colored, powdery deposits that accumulate during relatively long periods of time. These deposits can be removed with a dilute acid solution, such as vinegar, but cannot be removed effectively with water alone. The white plaque that often is seen on plumbing fixtures and in water tanks or on basement walls and floors is carbonates. If the substance does not dissolve with a few drops of water, try using a few drops of vinegar. If the substance does not dissolve in either water or vinegar, then it may be mold.
- There is extensive information on flood recovery at our NDSU Extension Service web site. Search for NDSU Flood Information on the internet.