Understanding and Controlling Mold

Where does mold come from?
What kind of health complications do molds cause?
Are molds toxic?
Is it true that modern buildings are more conducive to mold?
How can I discourge mold from growing in my home or place of business?
How do I get rid of mold?

Related Links

Where does mold come from?

Molds are microscopic fungi. Like dust and pollen, their spores float freely through the air. Lacking roots, stems, and leaves, molds can grow on virtually any organic substance so long as oxygen and moisture are present. Molds grow readily on many materials commonly found in homes, including insulation, carpet, wood, furniture, paint, clothes, food and paper. Mold begins when its spores land on a moist surface, germinate and begin to grow. Mold grows by gradually digesting (and thereby destroying) whatever medium it is growing on. Outdoors, this process serves a necessary function by aiding in the decay of fallen timber, dead leaves, and other debris. Molds also play a beneficial role in the production of antibiotics. Most antibiotics come from penicillin and cephalosporins , both chemical products of mold.
You can't see mold spores, but you can see and smell mold once the spores have germinated and the mold begins to grow. "Generally, molds give off a musty, unpleasantly medicinal and even slightly rotten odor." [Mike McClintock "How Household Mold Gets a Grip" from The Washington Post. September 12, 2002]. Molds come in a variety of colors (black, white, green, brown, and orange) and form a furry coating on the solid substance on which they are growing.

What kind of health complications do molds cause?

Opinions on the role mold plays in health complications vary widely. The general consensus holds that certain types of mold act as allergens which produce allergic reactions in sensitive individuals. When a mold sensitive individual inhales mold cells and they enter the respiratory tract, the person's immune system will attempt to destroy the mold cells as it would any infectious agent (such as a flu virus). The immune system responds by producing histamines to expel the mold cells from the body. Symptoms of this allergic reaction (often referred to as hay fever or allergic rhinitis) may include nasal discharge, watery eyes, sneezing, a sore throat, and itching.
While many types of mold exist, only a few dozen have been linked to allergies. The most common culprits are alternaria, cladosporium, aspergillus, penicillium, helminthosporium, epicoccum, fusarium, mucor, rhizopus, and aureobasidium. Harvard's mold expert, Harriet Burge, says mold only becomes a health issue when there's too much of it and that the "too much" threshold varies from one person to another. (Christopher Wanjek, "Tales About Rampant Toxic Mold Get Plenty of Attention, but Science Tells a Less Dramatic Story" from The Washington Post, September 17, 2002).
In some sensitive individuals, exposure to certain molds may trigger asthma attacks. In a few people, including those with compromised immune systems, the inhalation of certain mold spores may cause respiratory damage. People suffering from chronic obstructive pulmonary disease may actually develop mold infections in their lungs.

Are molds toxic?

The toxicity of molds is a controversial subject. A greenish-black mold named stachybotrys chartarum may, under certain conditions, produce toxic chemicals called mycotoxins. Stachybotrys grows only on cellulose containing materials (including paper, wicker, cardboard, fiberboard and drywall) and requires nearly saturated conditions. Consequently stachybotrys chartarum is found in vigorous quantities where moisture has accumulated from roof leaks, wall leaks, or chronic plumbing leaks. It is not unusual for it to grow in hidden places, such as behind walls, where a leak or moist conditions have gone undetected.

Even when stachybotrys chartarum is present in a building, it does not always show up in air samples. As a rule, it grows only where there are chronically moist conditions and its spores, when wet, are sticky and not readily aerosolized, meaning there may not be sufficient airborne spores to show up in an air sample. Even when airborne spores are captured in a sample, they do not always survive to the identification stage. Stachybotrys chartanum does not grow well on the standard media utilized for air samples and it is easily overgrown by other molds and bacteria. Therefore co-existing molds and bacteria may kill off any stachybotrys collected in the sample before its presence is identified. Stachybotrys is distinctive and can readily be identified from direct
tape-lift samples.
Individual reactions to the presence of stachybotrys chartarum vary widely. Some people are not affected at all while others may become seriously ill.

Is it true that modern buildings are more conducive to mold?

While mold spores have always been with us, today's buildings are sealed more tightly than ever before, which may contribute to the buildup of moisture. Remember, molds require moisture to germinate and grow. According to Steve Bauman (Healthy Spaces LLC in Austin) , "The shift of the home from a place of safe haven to the role of cause of disease has its roots in the energy crisis of the 1970s. Since the onset of the energy crisis in the mid- 1970s, the annual rise in the onset of asthma has risen at an alarming rate of increase in excess of 65% per year. This is directly attributable to the tight sealing of homes to save energy. Unfortunately, we've also `locked in' all the indoor air pollutants." [John Hall. "Mold and HVACR Systems" from the Air Conditioning, Heating, and Refrigeration News. June 24, 2002).

How can I discourge mold from growing in my home?

The key to discouraging mold is to keep your home clean, dry and in good repair. While mold spores are often present in the air, both indoors and outdoors, they require damp surfaces in order to grow. Once mold has seriously contaminated a home, it can be difficult to eradicate. While it's not always possible to predict and protect against unexpected water leaks, there are things you can do on a routine basis to discourage the growth of mold .
Maintain Plumbing

Have your plumbing inpsected annually by a reputable plumber.
Examine your pipes periodically for rust or white lime deposits which may indicate a slow leak.
If you find a leak in your plumbing, shut off the water supply and call a plumber. Water systems are under high pressure and a small leak can erupt into a larger one.
Pipes, fixtures, and tanks sometimes sweat during the summer, as vapor in the humid air forms condensation on pipes containing cold water. Generally, condensation will only form when cold water is running through the pipes, tanks, and fixtures. Once the running water stops, the pipes and fixtures will return to room temperature and the condensation will stop. Pipes, tanks, and other fixtures which continue to sweat for hours after the water has been run may be symptomatic of a leak or of a tank valve needing readjustment. Sweating pipes can be wrapped with an insulation material to prevent condensation and the formation of moisture.
In the winter, a major cause of plumbing leaks is burst pipes. During a hard freeze, water in the pipes freezes and expands and can potentially shatter the pipes, causing water to pour into your home. When leaving town in the winter, consider turning off your water at the shut-off valve, then run all your faucets to drain your pipes. (Remember to turn all the faucets off before you turn the shut-off valve back on!). Note: if you drain your pipes, be sure to contact your electric or gas company for instructions on how to protect your water heater.

Maintain Your Heating and Air Conditioning System

Not only leaks but high humidity can encourage the growth of mold. Here in the Gulf Coast area, your air conditioner serves a dual purpose: to cool and dehumidify air. A poorly maintained air conditioner may not effectively dehumidify indoor air. Furthermore a poorly maintained unit is more likely to leak water (from clogged condensation lines, from a clogged emergency drain pan, or from a drain pan which has rusted through). Improperly sized equipment can also make a home more vulnerable to mold.
Make sure that your air conditioning equipment is properly sized.
A cooling system which is mismatched or air conditioning equipment which is too small will not adequately dehumidify your home. Click here to get a general idea of what size equipment your home needs. The most accurate way to determine proper equipment size is to have a licensed air conditioning contractor or one of his technicians perform a load calculation.
For different reasons, oversize equipment can fail to adequately dehumidify your air. Some people choose larger air conditioners than their homes actually require in the belief that a larger unit will cool down their rooms more quickly, will run less, and will therefore consume less energy. Yes, larger equipment will cool down the conditioned space more quickly. The problem is that the equipment will achieve the desired temperature and will shut off before it has had an opportunity to adequately dehumidify the air.

What is the ideal indoor humidity level?

That answer varies from one expert to another. The Center for Disease Control (CDC) recommends that household humidity levels be maintained below 40 percent. The American Lung Association recommends that indoor humidity be maintained between 40 and 50 percent. These low levels can be difficult to achieve during Houston's most humid months. However, keeping indoor humidity below 60 percent should discourage the growth of mold (assuming there are no leaks or other sources of moisture) and falls within Environmental Protection Agency (EPA) standards (30 to 60 percent) for indoor humidity levels.

Run your air conditioner

While you may wish to raise the temperature on your air conditioner a few degrees to save on electricity when you're out or when you leave town, don't shut it off if the weather is warm and humid. Running the air conditioner during hot humid months is vital to keeping humidity levels low and thereby discouraging the growth of mold. The same holds true for any vacant home you are trying to sell. It is much cheaper to air condition an empty house than it is to eradicate mold.
Have your heating system inspected each fall and your cooling system inspected each spring.
Annual inspections help to identify minor cooling and heating problems before they become major ones. To discourage the growth of mold, it is important that you keep your heating, ventilation, and air conditioning (HVAC) drip pans clean, flowing properly, and unobstructed. In the course of an inspection, a technician will check your system for any obstructions likely to cause water leaks or excessive condensation. While inspections are no guarantee against water leaks, they can substantially reduce the likelihood of such leaks.
During your spring air conditioning inspection, ask the technician to add algaecide tablets to your main drain. Algae growing in your drain pan or drain lines may clog the lines, causing the water to back up and leak into your attic or through your ceiling.

Keep the air flowing freely

Poor filtration can cause your air conditioning system to release moisture. To maintain optimal filtration, change your air filter once a month. If you use an electrostatic air filter rather than standard disposable filters, be sure to remove it and clean it monthly (a good rinse with the garden hose should do the trick).
Maintain air circulation around your outside condenser unit. Do not plant or allow heavy vegetation to grow around the unit. Keep any lawn adjacent to the unit mowed and take care not to blow grass clippings into the unit. Watch for and destroy any ant mounds around the unit.
The air conditioning technician who inspects your cooling system each spring will advise you if your coils have become encrusted with dirt. Dirty coils should be professionally cleaned so that your air conditioner can effectively cool and dehumidify your home.

Consider having an Mechanical Air Filter and an Ultraviolet (UV) Air Disinfection System installed

Mechanical Air Filters (aka HEPA Filters or Air Media Filters) capture up to 95% of airborne pollutants. In contrast, standard cardboard air filters are only about 15% effective at catching dust and airborne particles. Ultraviolet Air Disinfectant Systems shine an intense ultraviolet (UV) light on the airborne particles which pass through your heating and cooling system. UV light acts as a disinfectant by penetrating and reacting with the DNA of any airborne microorganisms, including mold spores. It is used in the food industry to keep foods and liquids free of germns during processing and packaging. While microbes are not vulnerable to the natural UV levels found in sunlight, the UV light emitted by an Ultraviolet Air Disinfectant System is many times stronger than that emitted by the sun.
Note: both Mechanical Air Filters and Ultraviolet Air Disinfection Systems require maintenance. The Mechanical Air Filter contains a specialized filter which should be changed at least once a year. Likewise, Ultraviolet Air Disinfection Systems utilize UV lamps which must be changed about once a year (their average lifespan). Some UV systems come with an alarm which alerts you when the UV lamps require replacement. When consulting an air conditioning contractor about the installation of a Mechanical Air Filter and / or a UV Air Disinfection System, ask him about the cost of annual maintenance (replacement parts and labor).

Other Home Maintenance Tips to Discourage the Growth of Mold

Vent moisture-generating appliances, such as dryers, to the outside where possible.
Make sure your home is well insulated
While floods, leaks, and plumbing problems are obvious sources of moisture, a less obvious source is temperature differentials within a building. Temperature diffierntials occur where relatively warm, moist air comes into contact with relatively cool surfaces. Any water vapor in warm air is prone to condense on cool services. This is what makes a glass of ice water 'sweat' on hot humid days. When a ceiling lacks insulation, the warm upper air may condense on the higher portions of the walls, creating a moist surface conducive to mold. Likewise, non-insulated refrigerant lines in a hot attic may sweat and drip moisture onto the woodwork or insulation below. Refirgerant lines may be insulated to prevent condensation.
Don't allow your foundation to stay wet.
Provide drainage and slope the ground away from the foundation. Keep your foundation clear of leaves and pine needles. Mold thrives in damp organic material.
Regularly clean out gutters
Mold grows in damp, decaying leaves. The more leaves your gutters collect, the less able it will be to drain water away from your house and the leaves themselves make a perfect media for growing mold.
Keep your kitchen and bathrooms clean and dry
During and immediately after running showers and bath water, open your bathroom window or run the ventiliation fan. After showering, leave shower curtains spread their full length so they can dry more quickly. Scour sinks, tubs, shower stalls, and countertops regularly with bleach based cleansers. Molds thrive on soap and other films that coat tiles and grout.
Clean garbage pails frequently with one ounce ordinary laundry bleach diluted in a quart of water. Do this outdoors to avoid inhaling bleach fumes.
Clean refrigerator door gaskets and drip pans with a bleach based cleanser.
Regularly mop floors with a bleach based solution. Consider replacing bathroom carpets with tile or linoleum.
Throw away or recycle old newspapers, clothing or bedding.
Mold readily grows on paper and fabric. Newspaper, clothing, and bedding stored in the garage or attics are more prone to mold because your heating and cooling system doesn't reach (dehumidify) these areas. Dry clean rather than steam clean your carpet.
Steam cleaning your carpet introduces a tremendous amount of moisture into your home and temporarily increases your home's humidity levels, making it more conducive to mold. If your steam cleaned carpet takes more than 24 to 48 hours to dry, mold spores may begin to grow in its fibers. Just as there are professional steam cleaners, there are also professional dry cleaners who will come in and clean your carpet. If you like, you can dry clean your carpet yourself. Dry cleaning kits are available at some hardware stores and vacuum cleaner specialty shops. Dry cleaning will not remove existing mold from your carpet. (Mold infected carpet should be removed and replaced). Dry cleaning is simply a preventative measure - a low moisture alternative to steam cleaning.

How do I get rid of mold?

Technically, it's impossible to completely eliminate mold; invisible to the eye, the spores exist in the air both outdoors and indoors. However you can eradicate visible mold and prevent mold from growing. If you are treating a home for mold, you must first eliminate or fix whatever is causing the moisture. Next you must clean or replace all mold infected items. Finally you must have your air conditioning and heating equipment and ducts inspected for mold.
Attacking Mold Yourself versus Calling in a Professional
If you have identified and eliminated the source of moisture and the mold growth covers no more than thirty square feet inside your home or place of business, you may be able to remediate the contaminated area on your own. However, if you suffer from allergies, asthma, or respiratory disease or are immune depressed, you should not personally engage in any mold removal project no matter how small. While written primarily for remdiators of schools and commercial buildings, the EPA's booklet Mold Remediation in Schools and Commercial Buildings contains useful information on restoring homes and other buildings infected with mold. You can order a free copy by calling the EPA Indoor Air Quality Clearinghouse at (800)-438-4318 or can read the on-line version.
If you remediate your home yourself, you should have your heating and air conditioning system inspected by a professional for any evidence of mold contamination. Generally, once mold begins growing in a building, its airborne spores will circulate into the heating and cooling system and may contaminate the system's ducts and mechanical equipment. For details on steps a licensed contractor should take to remediate your heating and cooling system, see below.

Cleaning and Replacing Mold Contaminated Surfaces and Items

Identify Which Items Can be Effectively Cleaned and Which Must be Replaced
Mold can be destroyed and cleaned off non-porous materials, such as metals, hard plastics, and glass. Semi-porous materials such as wood, plaster, and concrete, if structurally sound, can often be cleaned and reused as well. However mold cannot be effectively removed from pourous items such as carpet, rugs, upholstery, ceiling tile, wallpaper, and mattresses. Such items should be removed from the home and replaced.
Precautions to Reduce Personal Exposure
During a mold removal and remediation project, the mold spore count in the air can increase 10 to 1,000 fold. Consequently, you should take the following precautions:
Wear an N-95 particulate respirator or breathing mask approved by the National Institute for Occupational Safety and Health. The mask should cover both your nose and mouth.
Wear gloves.
Wear goggles.
Wear protective clothing which can be laundered with chlorine bleach or which can be discarded upon completion of the project.

Step by Step Instructions for Cleaning Mold from Non-Porous and Semi-Porous Surfaces
North Carolina's Public Health Division offers the following instructions for cleaning mold from non-porous and semi-porous materials:
First, wet the moldy area down by spraying lightly with a water-and-detergent solution to help keep mold dust and spores from getting into the air. A high-efficiency particulate air-filtered (HEPA) vacuum cleaner can also be used to help in removing surface mold growth and removing the spores from nearby materials.
Using a non-ammonia soap or detergent and hot water or commercial cleaner, thoroughly scrub all moldy surfaces. Rinse the scrubbed surfaces with clean water. A wet-dry vacuum may be used to collect excessive water. After cleaning, a disinfectant solution such as household bleach and water (¼ to 1½ cup liquid chlorine bleach to one gallon of water), can be applied to the affected surface. Never mix bleach with ammonia - toxic gases can be created. Follow all label directions on all products used in this step. Make sure the area is well-ventilated when using disinfectant solutions. For this step to be most effective, the disinfectant solution should be allowed to stay on the surface for 6 to 8 hours and the solution should be allowed to dry naturally.
After cleaning and disinfecting, the affected surfaces should be dried as quickly as possible. The use of fans and dehumidifiers may speed up this process. If materials are not dried properly, the mold is very likely to re-grow. Moisture levels in wood should be less than 12 to15 percent prior to rebuilding, painting, etc.

Removing Mold from Your Heating and Air Conditioning System

In most cases, if mold is growing profusely inside a building, its spores will have contaminated the air conditioning and heating equipment. If your home undergoes mold remediation but its cooling and heating system is not professionally remediated, any mold living inside will be recirculated into the living space.
Mechanical Equipment
Any time mold is found inside your ductwork, it should be assumed that there could be some contamination in your evaporator coil and your heater assembly. Both the evaporator coil and the heater should be professionally cleaned. by a trained technician. To effectively clean the evaporator coil, the technician has to open the unit and clean it with a wire brush and commercial chemicals. For the furnace to be properly cleaned, the motor housing must be disassembled , the housing and the blower wheel cleaned, and the furnace then reassembled.
Ducts Duct systems are generally constructed from sheet metal, fiber glass, or some combination of the two. The general rule of thumb is that sheet metal, a non-porous material, can be cleaned and disinfected, whereas fiberglass insulation cannot. Duct systems constructed exclusively from sheet metal can be cleaned as can sheet metal ducts covered with exterior fiber glass insulation. However sheet metal ducts lined internally with fiberglass insulation cannot be cleaned nor can all-fiberglass ducts. These ducts, when contaminated with mold, should be removed, discarded, and replaced.
If you have your ducts cleaned, make sure that the company which performs the cleaning has the equipment and the expertise required to clean inside of all the ductwork. Many companies which advertise duct cleaning only clean up to the first four feet inside each grill. If they do not thoroughly clean the entire duct, the mold will not only continue to grow on the inside surface of the unreached ducts but its spores will be circulated through the system and back into your home. Furthermore, a fungicide should be released inside your ducts at the time they are cleaned.

Grills

You yourself can see whether there is mold growing on the supply air and return air grills. If there is, the grills should be replaced.
Insulation
If mold has been found in your home, the insulation in your attic should be inspected for mold, particularly if there have been any sources of moisture or water leaks in your attic. If your insulation is infected with mold, it should be replaced.
Once your heating and air conditioning system has been cleaned, do not run your heater or your air conditioner until after all other mold remediation inside your home or place of business has been completed.
Running your cooling and heating system before the remediation work has been finished will reintroduce mold spores into your system and recontaminate it. Because it is virtually impossible to eradicate all mold spores from the interior of a building, consider having an Electric Air Filter and Ultraviolet Air Disinfection System installed to contain and destroy any renegade mold spores.

Selecting a Mold Remediation Contractor

Mold has earned the nickname black gold because of the many contractors who are profitting from the remediation of mold contaminated buildings. There is presently no federal or state license for mold remediation contractors. Some do an excellent job; others are incompetent. The State of North Carolina's Public Health Divison offers the following helpful recommendations for selecting a contractor. Proposal - Ask the contractor to explain the nature of the diagnosis and/or mitigation he will perform. "This explanation should include the sequence of the investigation. A general systematic approach is usually more effective than relying on extensive air testing. The proposal should emphasize observations rather than measurements. Beware of contractors and consultants who want to conduct air sampling as a first step in determining the extent of your mold problem. There are currently no uniformly accepted standards that quantify how much or what kind of airborne mold is acceptable. A thorough visual inspection is the first and most important way to assess water damage and mold growth problems."
Interview - A contractor needs a preliminary understanding of the facts about what is going on in your building to determine whether he the skills, staff, and equipment required to perform effective remediation. A competent professional will ask specific questions about your situation to determine whether he can provide the services you require. Be alert and check for conflicts of interest.
Experience - Ask how much and what type of Indoor Air Quality (IAQ) work the contractor has done, to identify which employees will perform the remediation, and to provide you with a summary of their experience and their qualifications.
References - Request and contact references to verify that the contractor has helped them solve their IAQ problem.
Credentials - Presently there is no federal or state license for IAQ or Mold Remediation contractors. Find out if the contractor belongs to trade groups, holds any certifications, and whether he follow industry standards/guidelines in conducting mold evaluation and remediation. Two recognized groups which provide training, certifications, and guidance for water damage restoration contractors are the Association of Specialists in Cleaning and Restoration (ASCR) and the Institute of Inspection, Cleaning, and Restoration Certification.
Contract - The scope of the project should be identified. Communication between you and the consultant is essential, whether in person or by telephone. The frequency of status reports and meetings should be spelled out. The schedule, costs, and written report should be described.
Conflict of Interest - If you hire a consultant to investigate and identify a problem in a building, that should be all the consultant does. Do not hire a consultant who also provides remediation services. Although most consultants and contractors are honest, some may interpret environmental results (which are often somewhat uncertain) to steer you toward their services.

Additional Tips

Payment - If mold damage is covered by your insurance policy, ask whether the contractor will require payment from you or whether he will bill your insurance company directly. Remediation of Heating and Cooling System - Ask the contractor for the name of the individual or company which will handle the remediation of your cooling and heating system. Under Texas state law only a state licensed air conditioning contractor and his employees may open and the mechanical heating and air conditioning equipment, a necessary step in the remediation of your HVAC system. If the mold remediation contractor himself holds a Texas state air conditioning license, he shouild provide you with the license number. If he himself is not licensed to do air conditioning and heating work and sub-contracts the heating and cooling system remediation, he should provide you with the sub-contractor's license number upon request.

Related Links