U.S. E.P.A. (Environmental Protection Agency) on controlling relative humidity. Keep indoor humidity low. If possible, keep indoor humidity below 60 percent (ideally between 30 and 50 percent) relative humidity. Relative humidity can be measured with a moisture or humidity meter, a small, inexpensive ($10-$50) instrument available at many hardware stores.
U.S. E.P.A. (Environmental Protection Agency) “By controlling the relative humidity in a home, the growth of some sources of biological contamination can be minimized. A relative humidity of 30-50% is generally recommended for homes. Standing water, water-damaged materials, or wet surfaces also serve as a breeding ground for molds, mildews, bacteria, and insects. House dust mites, the source of one of the most powerful biological allergens, grow in damp warm environments.” Inspectors testing for mold in Miami or West Palm Beach should always look out for excessive dust because the combination of dust and humidity can easily lead to mold problems.
When struggling with home humidity problem or other issues
related to elevated RH, or excessive moisture in your air, you must act swiftly. In humid buildings the resulting attic condensation and the resulting mold and mildew that often grows on clothes in closets can get out of hand quickly.
Well Known AC Manufacturer (Carrier) Your home comfort system should provide both comfortable temperatures and comfortable humidity levels. It should maintain your home at the recommended levels of 40-60% relative humidity, preventing growth of mold and mildew and minimizing dust-mites, bacteria and viruses.
ASHRAE Standard 55-1992 They make the rules for all AC contractors and AC engineers to follow. Thermal Environmental Conditions for Human Occupancy sets guidelines intended to achieve thermal conditions that at least 80% of the occupants would find comfortable. ASHRAE humidity levels are recommended between 25-60%. http://www.yestek.com/faq.html#Anchor-ASHRAE-8432
Humidifier & dehumidifier sales and information website The optimum relative humidity level is generally considered to be between 40% and 50%. Levels anywhere between 30% and 60% is acceptable, however, below 50% is recommended to help control dust mites which are bad for allergy sufferers. http://www.humidifierinformation.com/optimum-humidity-levels.php
Well Known AC Manufacturer (Trane)
Most designers choose a dry-bulb temperature of 72°F to 76°F as the set point. To discourage microbial growth, ASHRAE Standard 62-1999 recommends a relative humidity of 60 percent or less during cooling. Therefore, select the dedicated AC unit to limit the relative humidity in all spaces to no more than 60 percent. Designing a dedicated ventilation system that limits the space relative humidity to a lower value (50 percent, for example) adds unnecessary cost because it requires larger equipment and increases energy consumption.
http://www.trane.com/commercial/library/vol30_3/implica.asp