Noticing foul smells while your HVAC system is running is a fairly common problem that can occur for several reasons. Luckily, it’s also something that can usually be overcome easily once you understand exactly what is producing the foul smells.

Issues That Can Make Your HVAC System Smell Bad

The most common cause of moldy and musty odors is mold growth on the AC evaporator coil or somewhere inside the air ducts. Odor-causing bacteria also often grow and build up on the evaporator coil, further worsening the issue. If the problem is related to the evaporator coil, you will usually only notice the unpleasant odors during the hotter parts of the year when your AC is running. If the musty or moldy odor persists throughout the year, it’s a sure sign that mold and mildew are present inside the ductwork.

Pests are also notorious for nesting inside air ducts. Any time you have mice in your home, there is a decent chance they will find their way into the duct system if it isn’t properly sealed. Birds can also sometimes get inside the attic and will occasionally build nests inside the ducts. If squirrels, rats and other larger rodents get into the attic or crawlspace, they may get into the ducts through any holes or even chew holes through flexible ductwork. Having pests in your ductwork means lots of urine and droppings. There is also a high chance of some of the pests dying and decomposing inside the ducts, which will contribute to the foul odors you notice.

Prevent Condensation by Insulating Your Air Ducts

Condensation is one of the main contributors to mold and mildew. Although it more commonly forms on the outside of the ducts and causes them to “sweat,” condensation can also form inside the ducts. The main reason condensation forms is due to a difference in temperature between the air flowing through the ducts and the air surrounding them. In the Sacramento area, ductwork condensation is usually a bigger issue in the winter when the weather tends to be wetter and more humid.

Attics and crawlspaces are unconditioned. This means they don’t receive any heating or cooling and tend to be hot in the summer and cold in the winter. In the winter months, the cold air will cause the sheet metal ducts to become quite cold. When your heating system turns on, water vapor in the warm air moving through the ducts can easily start to condense when it encounters the cold metal.

This combination of moisture and heat can quickly result in mold and mildew starting to form. The only effective way to prevent this issue is to make sure that all the ducts located in the attic or crawl space are fully insulated. Insulating the ducts blocks out the cold air. This means that there will be much less of a difference in the temperature of the duct and the air flowing through it, which should prevent condensation from forming.

Eliminate Mold and Bacteria With Germicidal UV Lights

Germicidal UV lights are the best choice for eliminating mold and bacteria growth and overcoming musty and moldy odors. Coil-sanitizing UV light units shine on the evaporator coils 24 hours a day throughout the entire air conditioning season to kill any mold and bacteria that are present and prevent them from returning.

There are also air-sanitizing units that will destroy mold, mildew, bacteria and viruses in the air as it moves through the ducts. This type of unit is great if you have an area in the duct system that is prone to condensation and mold growth, and it will also improve the air quality in your home and keep you healthier. Unlike coil-sanitizing lights that remain on 24 hours a day during the hotter months, air-sanitizing lights work year-round and are wired to turn on and off when your HVAC system does.

The reason that UV lights are so effective is that ultraviolet light damages the DNA of almost any organic microorganism. When the light hits mold spores, bacteria or viruses, it significantly alters them, so they’re no longer able to reproduce and spread.

Seal Up Duct Leaks to Reduce Condensation and Keep Pests Out

Air ducts tend to start leaking over time. The duct branches can start to sag and pull loose, and the foil tape used to seal gaps between different duct sections can also degrade and no longer stick properly. Although most ducts are made of galvanized sheet metal that is fairly resistant to rust and corrosion, condensation can still slowly corrode the metal and lead to holes developing.

Resealing your ducts and repairing or replacing any damaged sections can provide several important benefits. The biggest benefit is that it will help prevent energy waste and reduce your heating and air conditioning bills. Making sure your ducts are properly sealed can also help prevent odors by ensuring pests can’t get in the ductwork. Air leaks also increase the chances of condensation forming, which is yet another reason it’s important to have your ductwork inspected to ensure it’s fully sealed.

Have Your Ductwork Professionally Cleaned

The ductwork in most homes is quite dirty and filled with lots of dust, lint, hair and other debris, and all this debris can also result in the air coming out of your vents smelling dirty and musty. Professional duct cleaning can also help in this regard by removing all the debris. Pests also tend to be attracted to dirty environments, and having your ducts cleaned will also lessen the chances of insects, mice and other pests living and nesting in the ducts. The technician will also remove any dead pests, droppings and nesting materials from the ducts, which is why it’s a good idea to have your ducts cleaned if you’ve recently had a pest infestation.

Install a Whole-Home Air Purifier

A whole-home air purifier is a great option for both overcoming foul odors and improving indoor air quality. Another reason why the air coming from your HVAC system doesn’t always smell great is simply that the system constantly circulates airborne pollutants and chemicals as it runs. Installing a whole-home air purifier can be a huge help as it will work to filter or remove most of the pollutants, contaminants and impurities from the air moving through your ductwork. Some air purifiers also have an activated carbon filter that is specially designed to eliminate foul odors so that your home always smells fresher and cleaner.

Huft Home Services is a top-rated HVAC contractor specializing in indoor air quality and the full range of heating and air conditioning services. We install a wide selection of air quality equipment including UV lights, air purifiers, humidifiers and dehumidifiers, and we also offer professional plumbing and electrical services for residential customers in the Elk Grove, Sacramento and Yuba City area. For more information on the ways you can eliminate and prevent foul odors from your HVAC system, give us a call today.

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