Keeping the relative humidity at 70% indoors is not a good thing. That’s about the threshold where mold can really take off. If your thermostat is set to the fan-on position all summer, it’s possible to have a mold factory in your home. So if you’ve been told to run the fan continuously by someone who sold you an electrostatic filter, UV lights, or some other indoor air quality device, you may not have been given the complete story on how such products affect the air in your home. With the fan running continuously, the air passing over the warming coil will evaporate the water and put it right back into your house.
Read the entire article here: How Your Thermostat Can Grow Mold and Make You Uncomfortable