A school system finding mold in the buildings in which kids work and study every day is a major issue and one that will likely have the parents speaking out. After all, mold can be extremely harmful to the respiratory function of young children, particularly if those kids have allergies, asthma, or other underlying respiratory-related conditions.
This is just what happened recently, though, when high humidity levels were detected as part of an IAQ test at a high school. The high humidity caused alarm, and, sure enough, it was verified that mold growth was present in the building.
This high school was located in the southern portion of the country, where cooling systems would be in place to feed the classrooms. Cooling and air conditioning systems that are not operating efficiently can often result in unsafe humidity levels. They can create a very humid, cool environment, and, therefore, can lead to mold growth. Chances are very good that this is exactly what the high school is contending with.
The system can safely cool the air to 55 degrees, but the returning air must be reheated to between 68 and 70 degrees, in order to dry the air before it is circulated back to the space. Humidity control can also be achieved with mechanical cooling when used in conjunction with mixing boxes. This would provide cool, dry air to the classrooms. This would rely on a duct mounted humidity sensor, in order to ensure that the air remains at the correct humidity level.
With a humidity set point programmed into the system, damper position can be automatically adjusted to allow more- or less air flow into the mixer, thereby maintaining the appropriate humidity levels. The Mitchell Instruments DT282 Digital Relative Humidity & Temperature Transmitter for Duct Installation is a low cost solution for humidity control in any AHU system.