What is Mold?

Mold is alive, but it is neither a plant nor an animal. Mold is a type of fungus. It is part of a group of living organisms that are very common and serve an important role in the environment. Penicillin, an antibiotic that has saved many lives, is a type of mold, as is yeast.
However, mold can grow on bread and other types of food, making it unfit to eat. Mold can grow on the walls, floors and ceilings of your home as well as on your personal possessions. People often refer to some household molds as mildew, although the term also can apply to molds found outdoors.

How does mold enter a home?

Mold spreads by creating reproductive cells called spores and sending them into the environment. Mold spores are too small to detect with the naked eye. They are everywhere around us and you cannot avoid being exposed to them.

Mold spores travel in the air and attach to people's skin, clothing, shoes, shopping bags and belongings. Other ways spores can enter your home invisibly are: through open doors and windows, through your home's heating, ventilation and air conditioning system, and on the fur of a pet.

Once spores enter, they can settle onto carpeting or other surfaces inside your home. You cannot keep spores out of your home, but regular home cleaning and maintenance often can prevent mold problems before they arise.

How does mold grow?

Mold seeks MOISTURE, WARMTH, and FOOD, and all three conditions are necessary for it to grow. Mold is most likely to find a place to grow in a bathroom, basement or kitchen, but it can grow in other rooms if conditions are favorable. The climate where you live and the living habits in your household can affect the ability of mold to grow.

Mold spores can thrive and reproduce in wet or damp parts of your home: areas that have had flooding or where leakage has occurred in roofs, pipes, or walls, or areas around house plants, especially ones that sometimes are over-watered. In just 48 hours, a moist environment combined with room-temperature conditions and an organic food source can lead to mold growth.

Some places where mold can grow in your home are:
carpet, drapes, upholstery, leather, wood products, clothing, paper, cardboard, books, rags, wallboard, cloth, ceiling tiles, ductwork, paint, wallpaper, household dust

After it gets the food it needs, mold can move to virtually any kind of surface. Mold prefers temperatures between 40 and 100 degrees Fahrenheit. If a warm enough area in your home is humid or damp and contains items that mold likes to eat, your home could develop a mold problem.

Is it possible to have a home tested for mold?

Yes, but health agencies and experts do not recommend testing houses as a first line of detection and prevention. Mold testing can be expensive and time consuming, and it usually requires special equipment and trained technicians to obtain reliable results. Once you determine the level of mold in a home, there are no standards for judging if the level could cause problems for the occupants or when a house is clean. But most importantly, you probably will not get the results from your mold test for a couple of weeks, during which mold problems could become significantly worse. If you think you see or smell mold in your home, you immediately should clean the affected area and not wait for test results.

If you have your home tested, a technician will have to take an outdoor air sample at the same time as the indoor sample. This will allow the technician to determine whether the number of spores inside your home is significantly higher than the number outside your home. A higher indoor level could mean that mold is growing indoors. Before hiring a technician, check with your local health department for recommendations of a qualified laboratory, technician or industrial hygienist.

Are there risks associated with having mold in a home?

The growth of any type of mold in a home is never acceptable. Your safest and most prudent course of action is to treat all molds with caution and to remove them from your home as soon as possible.

In the spring, some people experience no health effects from the increased amount of pollen in the air, while other people have serious allergic reactions. The same is true with mold spores, both inside and outside a home. Some people experience little or no reaction from high levels of exposure to mold spores. Other people exposed to low levels can have allergic responses, including asthma, stuffy or runny noses, eye irritation, fever, wheezing, inflammation in the lungs, and skin rashes.

These same symptoms can be caused by a variety of allergens. If you experience the symptoms, you should not automatically assume that your home has a mold problem.

Healthy individuals usually are not vulnerable to health problems from airborne mold exposure. If you have concerns about possible health and safety issues regarding mold, immediately contact a medical professional and/or your local government health authority for guidance.

How do I know if my home has a mold problem?

If mold is growing in your home, you most likely will be able to smell it. Have you ever walked into a room that has a musty or earthy odor? You probably are smelling mold. Sometimes, you can see the mold on the surface of an object. In such cases, the item may be discolored or look as if it has smudges or blotches.

Often, you will not be able to see mold that is causing an odor. The mold could be growing behind walls, underneath carpets, or in other hidden areas. Mold growth is common in areas of a home that are damp or have suffered water damage. You should be especially concerned about the growth of mold if your home has had:
a flood, a sewer back-up, an overflowing toilet, leaking pipes, a leaking roof, leaking windows, humidifiers and any other serious water-related problems.

Some of these situations can result in the growth of bacteria, which also can cause musty odors and health problems.

Once materials become wet, mold can begin to grow within 24 to 48 hours. If your home experiences a water-related problem, clean and dry any wet or damp areas as soon as you find them. If you live in a rental property, immediately report water problems to your landlord.

The earlier you can detect the growth of mold in your home, the better a chance you have to control it. Early detection and treatment are very important. If you smell a musty odor in your house, start looking for the source immediately and remove it as soon as you find it. Prevention and early detection may save you from paying much greater cleanup and repair expenses later on. If you own your home, damage from mold and the cost of removing mold might not be covered by your homeowner insurance. (Read your policy or call your insurance agent to find out.)

If my home has not had a flood or other serious water problem, does that mean it is unlikely to have excessive moisture?

Many sources can add moisture to the air in your home. When you go outside on a cold day and can see your breath, you really are seeing moisture coming from your lungs as a normal part of breathing. Breathing and perspiring send moisture from your body into the air of your home. Other sources are:
Taking a shower or bath, Boiling water or cooking, Washing dishes and letting them dry on a drainboard, Hand washing clothing and hanging it to dry indoors,
Operating certain types of appliances, such as a clothes dryer that is not vented to the outdoors, Having house plants

Just because the activities listed above can increase moisture in your home does not mean you should stop doing them. You still can cook food, hand wash clothing, take showers and keep house plants. Simply make sure your normal living patterns do not result in an excessive amount of moisture build-up in your home.

How can I prevent mold from growing in my home?

While mold spores are all around us, mold growth can be prevented. As mentioned earlier, mold growing in your home requires MOISTURE, WARMTH, and FOOD. Depriving mold of any of these three items will stop it from growing, but it will not kill the mold that is already there. Mold spores will remain dormant, and if the moisture, warmth and food all reappear, mold will begin to grow again.

The most important steps in controlling mold growth are to clean any existing mold and to eliminate excessive moisture. You can take numerous precautionary steps:

Vacuum and clean regularly to remove possible sources of mold growth. Pay special attention to bathrooms and other areas of your home that are likely to generate a lot of moisture.

In portions of your home that are susceptible to moisture, use area rugs or washable floor surfaces rather than wall-to-wall carpeting. If you use area rugs, launder them periodically.

Do not store materials such as paper, books, clothes, or other possible sources
of food for mold in humid parts of your home.

Repair water leaks in your roof, windows, or any other part of the home as soon as possible.

Clean refrigerator drip pans regularly according to the manufacturer's instructions. If your refrigerator and freezer doors do not seal properly, moisture can build up and mold can grow there. Remove any mold on the door gaskets and replace faulty gaskets.

If you live in a house, make sure that your gutters and downspouts are clear of debris that may block the flow of water from your roof. Make sure the area under your downspouts is properly graded so that rainwater from the roof flows away from your foundation. Splash blocks can help rainwater to flow in the proper direction. If necessary, extend your downspouts.

Make sure other areas around your foundation are graded so that rainwater does not flow toward the house. Do not put gardens or plants too close to your foundation so that watering them could cause water to flow toward your house. If you water your lawn with a sprinkler, make sure the water does not hit your house or the area next to the foundation.

In the kitchen and bathroom, open windows or use exhaust fans when engaging in activities that produce moisture. Exhaust fans should be vented to the outdoors and not to an attic or crawl space.

If you have a clothes dryer, make sure it is vented to the outdoors.

If you use a humidifier, make sure it does not produce an excessive amount of humidity. During the summer, 60 percent relative humidity or lower probably will prevent condensation and mold growth in most parts of the country, but that is too moist for the middle of winter, when 40 percent relative humidity or lower will prevent condensation on windows.

If you live in a house with a basement, consider using a dehumidifier there. The cool basement floor and walls can be a source of moisture build-up.

If your home has an attic, make sure it is properly insulated and ventilated.

If you have a crawl space under your house, cover the soil in the crawl space with waterproof polyethylene plastic. If your crawl space is ventilated, close the vents in the summer and keep them open in the winter.

If you have water problems in your basement or crawl space, clean up affected areas as quickly as possible and take immediate steps to resolve the source of the problem.

How can I determine the level of moisture in my home?

Weather forecasters talk about the relative humidity outdoors. Likewise, the inside of your home has a relative humidity, which is a measure of the moisture content in the air. Hardware stores sell instruments to measure the humidity inside your home.

Humidity is an important factor affecting the comfort level in your home. Have you ever awakened in the middle of a winter night to discover that your throat and nose feel very dry? That could mean the humidity in your home is too low. To remedy the problem, some people use humidifiers, which are designed to raise the humidity in a home. Your goal should be to have enough humidity in the air so the members of your household can stay healthy and comfortable.

Too much humidity can cause droplets of water to form on your walls, floors and windows, which can lead to mold growth. This formation of water droplets is called condensation. It occurs when warm moisture comes in contact with a cool surface. If you pour a glass of ice water and leave it on your kitchen table, the glass soon will begin to sweat. The sweating does not come from inside the glass. It is created when moisture from the air condenses when it comes in contact with the cold outer surface of the glass.

A sign of excessive humidity in a home can be condensation on the inside of windows, especially if you have double- or triple-pane windows. If condensation is present for prolonged periods, take steps to reduce the level of moisture or increase ventilation in your home. Condensation also can result from the use of unvented fuel-burning appliances, such as kerosene heaters or wood-burning stoves. If you use such appliances, have them inspected by a professional contractor or a utility company representative.

Another sign of excess moisture could be the warping of floors or difficulty in opening wood windows and doors. In such cases, the moisture from the air is absorbed into the wood, causing it to expand.

How can I control the humidity in my home during the winter?

Mold growth on inside walls can occur during the heating season, especially on the surfaces nearest the outside of your home. Moisture traveling through the air from the bathroom, basement, kitchen or other sources may condense when it comes into contact with a cold wall. By having well-insulated walls, you not only can save energy, but you also can reduce the likelihood of condensation and mold. You can raise the temperature of your walls by increasing the circulation of warm air from your heating system.

During the heating season, an indoor humidity level below 40 percent will prevent condensation in homes in most parts of the country. A lower level of humidity or extra insulation may be needed to prevent condensation in homes in very cold climates.

How can I control the humidity in my home during the summer?

Humidity has an important effect on comfort during the summer. Some weather forecasters in the summer talk about the comfort index, which attempts to show how much hotter the air temperature is likely to feel to you because of the humidity. The higher the humidity, the hotter you will feel. One of the ways air conditioners operate is to remove humidity from the air, which makes you feel cooler.

If you live in an area with high humidity, be careful about leaving windows and doors open during the summer. This will allow moisture from the outside air to enter your home. A way to control indoor moisture during humid summer months is to run an air conditioner and/or a dehumidifier. If you use a dehumidifier, clean it often. Also, empty it daily or have it drip directly into a drain.

Warm air can hold more moisture than cold air. Therefore, when your home is warm in the summer, more moisture is likely to stay in the air rather than condensing on the surfaces of walls and windows. In most climates, keeping an indoor humidity level below 60 percent in the summer probably will prevent condensation and mold growth.

Even though your air conditioner removes moisture from the air, the areas around your air conditioning system can be a source of water build-up. Make sure the drip pan on your air conditioner has not overflowed, and check near your air conditioning system for traces of dampness where mold can grow.

How can I get rid of mold problems in my home?

After you have addressed any water and humidity problems with your home, you then can work on removing mold. If you need to clean an area of mold in your home, keep the following precautions in mind. To clean areas larger than 10 square feet, consult an industrial hygenist.

When handling or cleaning moldy materials and cleaning solutions, wear protective gloves, eye goggles, a N-95 respirator, and dress in long sleeves and pants that can be easily removed in the work area and laundered.

Minimize exposure to mold spores by using a respirator designed for particle removal for protection against inhaling mold spores. Respirators can be purchased from hardware stores. Be advised that such respirators will not protect you from fumes.

Make sure the room is properly ventilated while you are cleaning.
Start by trying to remove a small amount of mold to determine if you will have a health reaction to either the mold or the cleaning products. If you have a reaction, or if your home has so much mold that you cannot manage the cleanup on your own, contact a professional experienced in cleaning mold in homes. You also may need to hire a professional if mold is growing in an area of your home that is difficult to access, such as in ductwork, or if there is more than 10 square feet of area affected by mold.

Make sure you prevent the spores and mold-contaminated dust from going into other parts of your home by hanging plastic sheeting to separate the area. Use polyethylene sheeting ceiling to floor around affected area with a slit entry and covering flap, and maintain the area under negative pressure with HEPA filtered fan unit. Also, block supply and return air vents within the containment area.

Place the moldy items, cleaning rags and anything else that comes in contact with the mold in airtight plastic trash bags. Seal the bags before disposing of them.

When you finish cleaning, immediately wash the clothing you were wearing.

How can I clean and restore all the items in my home that have been affected by mold?

Follow the guidelines below to clean areas affected by mold that are less than 10 square feet. For larger areas, contact an industrial hygenist.

Books and papers: After the item has thoroughly dried, use a High-efficiency particulate air (HEPA) vacuum. Dispose of the contents of the HEPA vacuum in well-sealed plastic bags.

Carpet and backing: Wet vacuum the surface. Iin the case of porous materials, some mold spores/fragments will remain in the material but will not grow if the material is completely dried. Steam cleaning may be an alternative for carpets and some upholstered furniture. After the item has thoroughly dried, use a High-efficiency particulate air (HEPA) vacuum. Dispose of the contents of the HEPA vacuum in well-sealed plastic bags.

Concrete or cinderblock: Use the same methods described in Carpet and backing.

Hard surface, porous flooring: (linoleum, ceramic tile, vinyl): Damp-wipe surfaces with plain water or with water and detergent solution(except wood —use wood floor cleaner); scrub as needed. Or, wet vacuum the surface. After the item has thoroughly dried, use a High-efficiency particulate air (HEPA) vacuum. Dispose of the contents of the HEPA vacuum in well-sealed plastic bags.

Non-porous, hard surfaces: (plastics, metals): Use the same methods described in Hard surface, porous flooring.

Upholstered furniture & drapes: Use the same methods described in Carpet and backing.

Wallboard (drywall and gypsum board): Use the same methods described in Books and papers.

Wood surfaces: Use the same methods described in Hard surface, porous flooring.