How To – Curing Musty Or Moldy Smells In HVAC Heating Systems

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    If you have a musty or moldy smell coming from your home’s forced hot air system that doesn’t seem to go away it is important that you take the time to inspect your heating system and cure the problem.

    Mold that builds up in your heating system is due to dampness. All of the surfaces in your home and outside your home are covered with small amounts of bacteria. Normally this bacteria is not a problem to your breathing or health but when it it is allowed to grow higher percentages of it in the air you breath can cause respiratory problems.

    Often you will believe you have a cold or children and the elderly can exhibit symptoms of asthma. Prolonged contact can cause longer term health problems that require doctor’s care.

    So, now that you know that moldy smells indicate a problem that you should take seriously lets look as some of the  steps can you take to make sure your HVAC forced hot air system is running at its cleanest and best.

    Finding The Smell

    The first thing you want to do is find the area where the smell is worst. Do you smell the mold coming from all of the vents in your home or only one or two?

    This is important because the mold may be present only in your bathroom and if that is the case you may have a moisture problem that is easy to fix.

    If the smell is throughout the home and equal in all areas you most likely have a problem in one of your return ducts that feeds air from your home back through the heating system to be reheated.  Again a (near) bathroom or even kitchen return duct is more likely a problem here because of moisture being returned into the system and feeding the mold.

    Inspecting the Insides of Your Heating System

    The first thing you need to inspect is your return air filter. This filter is on the in air side of your heater and can be placed immediately before the heater or in any main duct that feeds the heater.

    Remove the filter and hold it up to the light. It should be relatively clean and should not show a black discoloration of mold. If it does replace it immediately.  This could be your only problem but it probably is not so expect to replace the filter once again after you have cured the main problem.

    When inspecting your vents and ducts you will need a very strong flashlight or a 500watt halogen work light to get a good look. A mirror is also not a bad idea to see around corners and farther into the duct.

    Remove your feed duct registers that are located on the floors or lower on the walls of your room and look into the duct to inspect for any mold.  Also inspect the register for any mold buildup on the vent flaps.

    If you find mold in only one room vent register then you have narrowed down the problem to just that area. Additional inspection will be necessary in your basement and feed lines.

    Return Vents

    After you have inspected your feed vents you want to inspect your return vents. These vents are placed near the top of most rooms and hallways. You will need a screwdriver and probably a step ladder to take them off and get a peek inside.

    Return vents that are using the cavity of your walls to feed air back into your system are definitely areas that you must inspect well.

    If you have a leak on your roof or from plumbing and small amounts of water get into this area then mold will grow.

    Cleaning The Ducts

    If you do find there is mold in your duct work you may find that the only way to completely remove it is to disassemble your duct work and clean it outside with bleach and a pressure washer.

    You never want to introduce liquids into your duct work especially bleach while it is still connected to your heater. Bleaching mold will require that the surface is wet for a minimum of 15 minutes that can take a lot of liquid.

    If you are attempting to clean the duct work in place then you should remove at least one – 5 to 8 foot section of the  feed and return ducts that attach to your heater to remove all possibility of having liquid enter your furnace.

    Hiring The Work Out

    Although there are HVAC companies that can perform this work you may also want to look at a cleaning company that specializes in cleaning Heating Ducts. The cost for an initial service will be around $75 but if you have problems this is where the cost can go way up.

    If heavy mold abatement is required a specialist may be needed. At this point you are talking well over $1,000 for the service and you will really need to know whether the job they are recommending is necessary.

    At some point removing and replacing the duct becomes more cost effective but remember if its metal duct you can always remove it and bleach it until its clean.

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