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Question DetailsAsked on 9/15/2011

How do I handle mold in my a/c coils?

I have mold in my air handler inside the house. I have been told to remedy the situation by doing everything from installing a UV light to kill too mold, to installing an ozone air purifying machine, to ripping out the walls, etc. and re-installing everything again from scratch. I'm also concerned about the ducts containing mold. It seems that everyone has different information and states that their method for resolving the issue is most definitely the best.

Any experts on the topic that could chime in for me here?

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9 Answers

Voted Best Answer

Yes Jupiter. It depends on the severity of the situation, is the mold encapsulated in the insulation. If yes, than replace [insulation] it with new. Is it on the casing of the heater? If yes, clean it with a mold neutralizing metal cleaner. It's not a matter of finding something or someone to clean or address the existing mold. It's a matter of finding a contractor to rectify what is causing the mold grow. It's coming from excessive moisture in the air-handler unit. I can say with 100% surety you’re dealing with poor airflow and/or incorrect equipment sizing! Either issue will cause excessive icing of the evaporator coil, which leads to excessive condensate water in the system. The condensate will eventually overflow the drain pan leaving stagnant water in the air-handler housing, which leads to mold growth. I would not let any contractor do any kind of temporary repair, add any device like a UV light or air-cleaning product until the aforementioned is corrected. I talk a lot about this in my videos and on my website. It is the result of improper system design from unqualified contractors. There is a reason why some guys cost more than others, and this is one reason why!


Answered 9 years ago by Stans HVAC


Does the ozone system get installed directly in the box underneath the air handler or does it sit outside? I'm confused how it kills the mold inside the box that collects all of the air.

Thanks for the initial insights.

Answered 9 years ago by JupiterFL


first you have to take care the cause of the mold after that you can take care of the ducts. first the air handler you need a trusted tec to pull and clean your evaporator he pull out the unit soaks it down coil cleaning solutiom which would penetrate the coils and with the foaming action pushs out the dirt after a good soaking he should hose down the evap.until all the solution is wash away. second after the coil is pull and clean your tec should install a uv light in the supply side of your box. if you have an A shape coil a light should be installed on both sides that should take care of sanitising your system. about your concern with the duct system the uv lights should take care of any future mold. If you think there is mold in your ducts now call a good duct cleaning company who will take care of any soiling in your system. This will definitly take care of you health situation with your system. It might be a little expensive but compare hospitals it is cheap.




Answered 9 years ago by koolray


For heavens sake, Do NOT spray bleach, or put ozone in your home! Ozone is a pollutant. Bleach is a pollutant as well. Why treat the bleach with something that can cause you to devlope cancer or worse? An ultraviolet light system will perform well for treating a constant surface. Uv light will be pretty much in effective for any air that is moving. I would want to first, find out where the mold is coming from. This could most likely be caused by an over sized air conditioning system. That aside, the way to keep your air conditioning system free of mold would have 1 or more steps apply. The first step is we would want to prevent any mold spores from entering the system in the future. With that, an advanced air filtration system like the IQ AIR would be the answer. This system will virtually gather all of the contaminents from air and prevent them from entering the hvac system. This will also kill virtually all mold spores before they enter the system. The second part is to have a reputable HVAC specialist perform a precision tune-up and clean the heat removal system with a non-toxic sanitizing solution to rid the coil of the mold , dirt, dust, and bacteria that currently resides on the coils. The last thing is to add an air sanitizer that uses photo-hydro ionization to treat the mold throughout the home, and hvac system. This system is tested to be ozone safe and will work well in conjunction with the air filtration system. I am an HVAC design specialist with a commitment to providing the best indoor air to my clients. I research all things on the market and only choose to offer the best solutions. I have no direct ties to any manufacturers, and I have attended many classes on air quality. For your further studies, I would recommend researching Ozone, Bleach, Mold, IQ Air, is a great tool.

Answered 9 years ago by GlennJr


Since mold will corrode aluminum, but it does not feed off of aluminum, the mold is feeding off of something on the surface of the coils.

Mold requires moisture (actually excess humidity) and a food source. Dust and/or construction debris are the most common food sources for the condition that you described. I would suspect that either your AC unit housing is not properly sealed and is drawing outside contamination, your home's air ducts are dirty, or the air system has been ran without a filter or with an improperly fitted filter.

The moisture is typically related to the AC unit not having been properly installed (the unit must be level), there could be an internal corrosion problem, or the condensation drain line has become plugged.

We have successfully completed numerous AC mold remediation projects in the 11 years that we have been in business. The process involves determining what caused the mold, fixing the cause of the problem, removing the mold from inside the AC unit (remediation), cleaning and sanitizing the duct work, scrubbing the air inside the home and installing a disposable high performance air filter into the AC unit (Filtrete UltraAllergen Air Filter).

I hope this has been of help.

Daryl Choby
Moldex The Mold Experts
Scottsdale, AZ

Answered 9 years ago by Moldex - Scottsdale


Don't blow anything out unless you want mold spores going airborne and filling your lungs when you breath.

Pour straight undiluted Bleach into a spray bottle and spry the coils. The bleach will dissolve the mold and clean the coils. Be sure to ventilate the area while spraying as the bleach can burn your lungs.


Answered 8 years ago by Canaduct


Mold and bacteria grows when it has dandruff, sneeze spray and smoke from cooking available as food. These and other organic indoor pollutants collect in your cold, dark, wet air handler where all the conditions for life are just right (food, water and shelter). In order to stop this growth one of these elements must be taken away, food, water or shelter. The most inexpensive, most practical, easiest way to prevent this growth is by replacing your air filter with a quality filter every month (even if it says 3 mo on it). Here in Wesley Chapel (Tampa) we have very long, very hot, very humid summers and no chinese u v lights or spray chemicals can take the place of your filter changing diligence. Badly designed return filter systems can handicap you in this effort. Missized equipment is somtimes a problem also but the first step is with you and your fabulous filters....Mike

Source: Mike Reaka President, Wesley Chapel A/C Company

Answered 6 years ago by mreaka


Don't blow anything out unless you want mold spores going airborne and filling your lungs when you breath.

Pour straight undiluted Bleach into a spray bottle and spry the coils. The bleach will dissolve the mold and clean the coils. Be sure to ventilate the area while spraying as the bleach can burn your lungs.

Answered 5 years ago by Sophie


Wow there is a lot of advice here that is very mixed about mold the one thing i agree on is finding the source of the moisture the mold will grow when it is dark, cool and damp that’s all there is to it when the moisture in the home is nearing 45% and higher you can expect mold making sure the system is properly sized is ever so much more important than just preventing mold production proper sizing has a lot to do with your install and monthly bill lifespan of equipment yearly maintenance and so on as far as mold reduction and elimination the best set up i have used with the best research and results is a catalyst type UV lite i am sure it is against the rules to name company’s so i won’t do that however i will explain why the results are so good with certain UV systems catalyst types that create ionized-hydro-peroxides leave the duct work and seek out mold and bacteria which will fill the house by volume scrubbing the home and air clean over time this is exactly the same technology used in hospitals it is not a good idea to disturb the bacteria and mold with rags sponges and chemicals besides any cleaning you do will most likly have no effect because the spores have distributed throughout the home via the duct system mold generally does not stay in the duct in older duct systems mold can grow if there is moisture because it can eat the dust keeping and using good quality clean filters are a big help also a common problem is an improper condensate drain if it does not have a correct back grade or a proper vent and p-trap set up then not only with it drain poorly it will rust out your equipment by traping the moisture and again aid in mold production there are plenty of YouTube videos out there to show a proper condensate drain set up this is very common the bottom line is this the correct UV system combined with a properly installed central system is key remember CHEAPER IS NOT ALWAYS BETTER.

Source: Me

Answered 5 years ago by redshield


First of all,the panels to the airhandler should be removed to allow an inspection of the interior.Most likely, the drain pan needs a good cleaning.The evaporator coil and the blower wheel need to be inspected and cleaned if necessary.The inside should be thoroughly cleaned and sanitized with a commercial grade cleaner which kills any mold spores.A good cleaning can help keep the airflow problem down to a minimum if the system is designed properly.The next step would be to clean and flush the drainline.I would also recommend a better filter,one which would not restrict too much airflow.After this, the static pressure and refrigerant charge should be checked.

Answered 5 years ago by applac

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