Mold can appear in many colors, from white to black with numerous shades in between. It can also appear in different consistencies, from velvet to slimy, depending on how deeply the colony resides within its affected household surface. If you notice mold growing in your closet, the problem could be caused by several factors.
Fabrics such as clothes present a prime breeding ground for mold. Cotton provides "food" (or nutrients) for mold, and the absorbent nature of fabrics allows them to retain moisture. This combination of moisture and nutrients causes clothing to attract mildew (an early stage of mold growth). If you have moldy clothes hanging in your closet, the spores can easily spread and settle in new locations, such as on the carpet and on the walls of the closet. Always inspect clothes before putting them away, and never hang wet or damp clothing in your closet.
In seasons of high humidity, closets can prove conducive to mold growth, according to North Dakota State University professor Kenneth Hellevang. Closets along exterior walls have the highest risk, as excess water vapor accumulates in the dark isolated location. You can improve the air circulation to the closet by leaving the door open during periods of high humidity, and you can keep the humidity under control using a dehumidifier.
Moisture must exist in some form for mold to grow. If you can rule out humidity, inspect your closet for another source of moisture. Perhaps you have a leak in the ceiling resulting from a recent rainstorm. If the moisture appears to come from within the walls, contact a mold remediator immediately. This usually points to an internal plumbing problem, and you may have a larger mold colony growing inside the wall.
Mold grows from spores and can spread rapidly to new locations. If you cannot identify the source of your closet mold, it may have originated in a completely different location, such as above the ceiling. Mold seeps through wall boards and ceiling tiles, settling in new locations such as closets. Find exactly where the colony exists in your closet (for instance, you may notice dark patches on the ceiling), and determine whether you can access the other side (such as the attic) to find the root cause of the mold. Always wear a breathing mask when inspecting for mold.