overhumidification

Overhumidification refers to a condition in which indoor or process air contains more water vapor than is appropriate for the space or application. In many residential and commercial environments, prolonged relative humidity above about 60 percent is considered overhumidification, though recommended ranges vary with climate, season, and activity. Excess moisture can lead to surface condensation, which in turn fosters mold growth, musty odors, and damage to furnishings and assets.

Causes of overhumidification include inadequate ventilation and exhaust, malfunctioning or improperly sized humidification equipment, leaks and water intrusion, and sustained moisture sources such as cooking, showers, or plant transpiration in greenhouses. In industrial settings, process-generated moisture or poorly controlled climate conditions can produce similar issues.

The consequences extend beyond comfort. Health concerns include increased risk of respiratory irritation and allergic reactions for sensitive individuals. Material and structural damage can occur as wood warps or decays, paint peels, metal corrodes, and insulation loses effectiveness. Mold and mildew growth can degrade indoor air quality and trigger odor problems. In electronics, pharmaceuticals, archives, and museums, excessive humidity can compromise specimens, equipment, or products.

Detection and control involve monitoring with hygrometers and, when possible, dew point measurements. Common guidance suggests keeping indoor relative humidity roughly between 30% and 50% for general comfort and mold prevention, with some facilities allowing up to 60% in specific circumstances. Control methods include improving ventilation, using dehumidification or air conditioning, sealing leaks, improving insulation, and managing humidity sources such as baths, kitchens, and drying processes.