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Mildew is a type of mold, and is defined as a thin, superficial, usually whitish growth consisting of minute hyphae (fungal filaments).Mildew spores exist everywhere; however, they will not grow and spread unless certain conditions are met. Generally, the following conditions contribute to mildew growth:

• Mildew thrives on organic materials such as paper, leather, natural fibers, or surfaces coated with the slightest amount of organic matter such as food or soil
• The optimal growth temperature for mildew is 77°F to 88°F (20°C to 30°C,) though some growth may occur anywhere between 32°F to 95°F (0°C to 35°C)
• Mildew requires moisture. The optimal growth range for mildew is 70 to 93 percent relative humidity (RH). RH would have to be below 62 percent to stop all chances for mildew growth, although RH below 70 percent inhibits most mildew growth. A lower RH delays spore germination of mildew, reduces the rate of mildew growth, and lowers the number of cells produced.
• Mildew requires oxygen for growth

What problems are caused by mildew?

Mildew secretes an enzyme that decomposes organic matter, like cellulose and lignin, and therefore damaging cellulosic fabrics. Wood, paint, glue and leather can be damaged as well. Mildew is unsightly, and produces an unpleasant odor. Also, airborne mildew spores – tiny, lightweight “seeds” - are known to cause respiratory problems, common allergic reaction symptoms, nervous-system disorders and depression.

How does mildew form in an automobile?

If an automobile interior has become wet from a flood, suffered water damage due to a leak into the interior, or from windows were left down in the rain, the carpets, seats and other upholstery may have become wet. This can initiate mildew growth.High humidity, and water condensation also induces growth. Mildew can likewise grow on the exterior of a vehicle if humidity levels are high/condensation is present.

How to prevent mildew

Preventing mildew from occurring in the first place is the ultimate goal.

If an auto interior has become wet, the key to preventing mildew is to thoroughly dry it out as soon as possible. Using a dryer is highly recommended. Of course, it’s a capital idea to ensure the interior doesn’t become wet again, which may include repairing a water leak.

Sunlight is a good mildew inhibitor, however, the downside is UV rays can damage automotive paint, interiors, etc.

Air conditioning reduces humidity levels, and temperatures to levels that inhibit mildew growth. However, the vehicle may be stored outdoors. Or, it may be inappropriate to air condition a garage. Dehumidifiers can be used in a garage, however, garages usually aren’t very airtight so it the effectiveness may be limited.

In small enclosed areas where temperature and humidity cannot be controlled by air conditioning or dehumidification, desiccants can be used. Desiccants are materials such as silica gel or alumina that absorb moisture. A container can be placed in an auto interior to absorb excess moisture in the air.

Chemical mildew inhibitors aren’t recommended as no product will kill mildew and guarantee it will not return. As well, these inhibitors are toxic to people and animals.

Air circulation helps to keep things dry - avoiding condensation inside and on the vehicle. Air movement is excellent at removing moisture. When the air outside is drier than that inside, ventilation allows the dry air to enter, take up excess moisture and then is carried outside. When natural breezes are not sufficient, you can use electric fans placed in a window, set in a wall or vented to the attic to move air from the garage.

CarCapsule’s Evaporative Storage System (E.S.S.) technology is featured on all CarCapsule and ShowCase models, and uses air circulation to prevent moisture condensation in and on a vehicle. Condensation can form when there are rapid temperature changes in air temperatures. With E.S.S., inside and outside air are continuously exchanged so that it keeps the inside and outside air the same temperature. Since the atmospheres are similar it causes no mildew inducing condensation. Please note; it’s best to open your vehicle windows when parked in a capsule so air is circulated through the interior as well. Incidentally, outdoor versions of the CarCapsule seal the vehicle from rain and snow which avoids water entering the vehicle from leaks in the top, etc. in the first place.

E.S.S. can also eliminate moisture that may have been brought into a capsule, like dispersing a puddle of water created by a dripping wet car. A great example of moisture elimination can be seen at http://carcapsule.com/blog/now-you-see-it-and-now-you-dont-the-magic-of-ess/. A car can even be put away wet, and the fans will dry it.

How to remove mildew

If an auto interior is left wet and not quickly dried, mildew will flourish and the smell will become very unpleasant. You may presently be experiencing this issue. A professional automotive detailing company can usually eliminate the problem, however, doing the job yourself can provide satisfactory results as well.

Steps to remove mildew from carpeting

1. Fill a carpet cleaner with hot water.
2. Add the appropriate amount of carpet shampoo. Each vacuum is different. Some will use a separate compartment for the soap, and others add it directly to the water.
3. Use the upholstery attachment if necessary for small spaces.
4. Clean all of the areas that were affected by the mildew.
5. For additional cleaning power, add a small amount of household bleach. However, be aware that this may discolor the carpeting.
6. Once clean, rinse the entire area with clean water and vacuum away the moisture with a wet-dry vacuum.
7. Keep the car open and allow it to air dry completely.

Avoid using liquid odor or mildew eliminators or homemade solutions with liquids. Because it will be difficult to dry the carpet completely, you will likely extend or multiply your problem.

It’s best to wash the interior of your car on a hot, sunny day. Keep all the doors/windows open to allow maximum air flow and shorten drying time.

Removal of mildew from seat upholstery

1. Fill an empty spray bottle with distilled white vinegar
2. Spray the seat material until all of the mold surfaces are soaked. White vinegar will work on leather, vinyl and cloth-type seats without damaging the material. If the mold is confined to a small area, overlap the spray from one to two-feet in circumference around the area. For heavy contamination, spray the entire seat.
3. Let the vinegar soak for 10 minutes or more, allowing it to kill the mold
4. Use a wet-dry vacuum to suck up the moist vinegar, removing it from all seams and crevices.
5. Vacuum the carpet directly underneath the seats.
6. Let the interior air dry for 10 minutes
7. Use a damp cotton towel to wipe all the remaining vinegar residue from the seats.

Mildew Information Source:

1. How to Prevent and Remove Mildew, by Virginia Peart, University of Florida IFAS Extension, October 2001