If you’re a South Florida native, you’ve probably experienced a humidity bloom at one point or another. This is when mold blotches and spotting develops across surfaces of personal belongings and furniture. This is especially noticeable on leather goods, wood furniture and many other items typically found within a property. This spotting can sometimes be light, while in other situations it can overtake all belongings within a property within a few short weeks.

Now that we’re all on the same page as to what a humidity bloom is, let’s briefly discuss causation for a moment. Why do I have mold growing on my personal belongings? In an overwhelming number of instances, we find that the thermostat within a property has the the wrong settings in place. More specifically, we identify the fan setting to be in the ‘ON’ position. Why is the ‘ON’ setting such a bad thing? Let’s first discuss how an HVAC system operates, as then you’ll have a better fundamental understanding.

When an HVAC system is operating normally, an user will select a temperature setting on the thermostat and the system will work vigorously to achieve said temperature. Through this process, room temperature air will be drawn into the intake side of an air handler, where a condensing coil will essentially exchange the warm air coming in with cool air being exhausted throughout the property. The system achieves this temperature exchange by an outdoor unit pumping refrigerant through the system – which in turn rapidly cools the air, draws the warm air to the refrigerant making its way back outdoors and the cycle completes time and time again. As this process takes place, excess moisture from the air condenses on the coil and is then guided through a designated condensation pipe to the outdoors.

Continuing on with normal operation, a system will stop pumping refrigerant and cycle off once the desired temperature is achieved. There’s a period of time following this off cycle that the coil will condense moisture, which will continue to be collected and guided outdoors. Now, when a thermostat has the fan in the ‘ON’ position, there is one major flaw that occurs. Instead of the excess moisture on the coil making its way down through the condensation pipe and outdoors, it is instead being expelled back into the home by the continued stream of air from the fan. As compared to normal operation, where the fan is set to ‘AUTO’, constant circulation of air will lead to much higher humidity levels. With the increase in humidity, it’s only a matter of time before mold development begins.

While there are other reasons for the promotion of a humidity bloom indoors, the thermostat settings is the most common culprit. Some other contributing sources may be low refrigerant levels, windows being open while the HVAC system is in operation, dirty AC filters and even excess moisture from a leak. So, how do you ensure that you maintain healthy home status? Be sure that your thermostat fan setting is in the ‘AUTO’ position, change your filter regularly and service your system annually. You’ll likely require more frequent service for the cleaning of the condensation line, so specific service times will vary.