Treat areas prone to mildew, such as the bathroom tiles, with a fungicide aerosol spray.
Keeping mildew at bay
From eNews, June 10, 2004
Mildew stains are often easy to detect because of their dark color and musty odor. You can prevent this mold from growing rampant in your home this summer-that combination of warm temperature and high humidity is what it craves-with some tips from the University of Minnesota Extension Service. What is mildew? Mildew is a mold with spores that will grow and spread under certain conditions of moisture, warmth, and darkness. Mildew thrives on organic materials like paper, leather, and natural fibers such as wool, cotton, and linen. If left alone, it will continue to spread and stain textiles, books, walls, tile, and other surfaces in your home. Remember, even if you can't see it, mold can still be present.
What can you do? Keep surfaces clean, well ventilated, and dry. In closed areas, use a dehumidifier or desiccant--such as silica gel or alumina--to absorb moisture. Air conditioning can reduce the temperature and humidity in your home to levels that prevent mildew growth. Never leave damp or wet clothes in a bundle, on the floor, or in the laundry basket. Always wash and dry them promptly. If there are areas in the home in which you periodically find mildew, such as the bathroom and basement, treat these areas with a fungicide aerosol spray.
How can you tell if your home has excess moisture or above average humidity? Look for the obvious signs such as condensation on window surfaces, cooking and other odors that linger longer than usual, damp surfaces, musty smell, and mildew stains in areas where there is poor air circulation (such as corners, behind furniture, or closet walls). You can also measure the amount of moisture and humidity in your home by using a humidistat or sling psychrometer. You can buy them at a building supply store or contact heating contractors to run a humidity test for you. Edited from INFO-U, the University of Minnesota Extension Service's multilingual, prerecorded information service.