The presence of mold in an HVAC system is a common complaint.  Mold is a sneaky little bugger.  It can grow and proliferate and make building occupants sick without ever being seen.   And the fastest way to spread mold through a building is through a forced-air HVAC system.The reason this complaint is so common is that mold is always present in your buildings and your HVAC system to the extent that it is present in your building’s environment.   There will be more mold in humid weather and less in dry weather.   You will never get rid of it completely, but you can control it.   All it needs to grow is moisture and food.   Take those away and the mold goes away. for residential and light commercial mold remediation productsAccording to the U.S. EPA, you should routinely inspect your HVAC systems, not just for mold, but for moisture.   Look at drain and condensate pans to make sure they are draining properly.   If they are plugged, the moisture that accumulates will become a mold factory.  

Also make sure that all HVAC ducts and system components such as air handlers, blowers, plenums and the like are free of any moisture.If, despite regularly inspecting your system, you are still getting complaints about it (mold starts to grow in as little as 48 hours), here are some tips for cleaning it up:1.) Turn off your HVAC system.2.) Everyone involved in this cleaning should wear at least an N-95 respirator3.) Replace anything porous, such as filters or insulation that has become wet.  Double-bag the waste using at 6-mil or thicker plastic bags.4.) Use wet vacuums to clean out any standing water.5.) Use an EPA registered disinfectant labelled for HVAC use to clean non porous surfaces (Duct work, coils, plenums, pans, etc) of mold, mildew and other dirt. BBJ MMR-II ready-to-use disinfectant and mold cleaner will kill and remove mold, mildew and odor causing bacteria.6.) As an added measure, isolate each section of ductwork you clean with bladders so the spores you stir up during cleaning don’t spread to other parts of the system or the building.

Fog the area with an EPA registered disinfectant.7.) Apply a mold and mildew inhibitor to all components of the HVAC systems. Again, this must be EPA registered and specifically labelled for use in HVAC systems to limit risks associated with using the wrong chemicals and cleaners in HVAC systems. Goodway’s CoilShine-BC is EPA registered for use in HVAC systems to control mold growth for up to 2 years.8.) As a final step, HEPA vacuum anything that you cleaned up.Check out these other resources:A sick house is a house with a serious air quality problem. An area can be described as "sick" mainly because people who reside inside it for an extended period can develop symptoms of illness such as headaches, watery eyes, nausea, skin disorders, and fatigue. The illness causing factors vary and can include a build-up of air pollutants from household products, building materials, formaldehyde, and/or respirable particles. In humid climates, sick houses are usually houses with a serious moisture problem.

Moisture also plays an important role in promoting the growth and spread of mold (mildew). rheem 3 ton air conditioning unitMolds produce spores, tiny encased "seeds," that float in the air. my ac unit keeps tripping the circuit breakerWhen a home is severely contaminated, thousands of mold spores can be suspended in each cubic foot of air. furnace blower motor noise startupWhen people are repeatedly exposed to mold spores, they can develop allergic symptoms. Visible mildew and mold is easy to identify because of its discoloration and odor. Keeping humidity in a home low can help keep visible mildew from returning, but if mold spores get into the air conditioning system, they can settle in the air conditioning ductwork, along with dust and other contaminants, where you can’t see or smell them.

This is a worst case scenario because duct systems in humid climates are incubators for microbial pollutants like mold and bacteria. With the alternating high and low humidity conditions that regularly occur in air conditioning ducts during normal AC use, mold will grow, produce spores, and spread throughout the house. Effective filtering is a huge part of keeping ducts clean. If you have pets, plants, or other unique factors at play in your home, consider upgrading to a newer kind of filter the next time you swap them out. Newer filters can now remove smaller particles, and more of them as compared with the older fiberglass filters. By neglecting to clean or change your filters, the build-up of dust and dirt on air conditioning filters causes air to by-pass the filter and carry organic dirt and spores into the ducts. Leaks around duct joints in attics can also introduce dust and spores. Moisture in air ducts is nearly unavoidable, as the air leaving the evaporator becomes saturated as part of the AC’s normal process.

If you run your air conditioner for the majority of the year, this leaves little time for that saturation and moisture to actually dry up. High moisture can cause any dirt present in the duct to become caked on and provide an environment for mold to grow. The best way to address this issue is to either use the air conditioner less frequently or to clean the ducts regularly to clear out any caked on dirt and moisture. There are many different methods for cleaning ductwork, but because air ducts are such complex, closed systems, it is often difficult to maneuver equipment through them to clean or even locate every specific patch of dirt or buildup. Most methods involve the use of shop vacs and motorized brushes, and while a dedicated professional can remove a fair amount of dirt with these tools, it is time consuming and the worker is often limited by how far though the duct their equipment can snake. More expensive options clean using essentially the same principle, but with larger and more powerful equipment.