It's simple. People need air to breath. The air in the house needs to be refreshed, changed regularly. Using an exhaust system like a bathroom fan can accomplish that very effectively. It takes the air out of a polluting area like the bathroom where a great deal of moisture can be generated. In the process, it puts the house under a slight amount of negative pressure, drawing in fresher outside air.
The FNTC-VT20M control can operate any Fantech fan with a load of less than 2.5 amps that has been rated for solid state speed control such as one of the Fantech in-line fans. The flow can be set to meet the building code or ventilation standard such as ASHRAE 62.2. When the bathroom is occupied, the front panel button can be pushed, boosting the flow to full speed for 20 minutes, long enough to get rid of the worst of the moisture or odors.
As homes get tighter, Indoor Air Quality or IAQ, becomes increasingly important. To keep the building healthy and to keep you and your family healthy.