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Question DetailsAsked on 5/21/2017

Need to identify source of odor in home, Seems to come from vents when air kicks in. who do I call first,

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3 Answers


Smell and look around where your air intake is for the HVAC system - with central air (heat and cooling in same ducts, as is normal) that would be where your furnace air filter is.

Or if you have a separate air handler for your A/C or have a heat pump, then at the air handler filter (where the evaporator coil and fan are) for the A/C or heat pump. This is NOT the outdoor fan which cools the A/C or heat pump - it would be an air handler box feeding ducts into the house.

If there is no indication of the odor generally in the immediate area - due to moldy or fungusy basement or rotting framing/wood foundations or animal invasion or such, then is most likely to be mold and possibly bacteria / algae and in very extreme cases even fungal growth at the evaporator coil. Can be due to growth in the drain pan under the coil, blocked drain line causing overflow from the pan resulting in growth on the surface below it, or growth on the coil itself. In different cases can smell moldy, like mushrooms or other fungal growth, like rotten meat (from wood fungus normally), even on odor commonly called "stinky sock syndrome". For this, a Heating and A/C contractor to inspect/clean the coil would be your first choice as a Search the List category to find well-rated and reviewed vendor for your job.

Rarely can be mold or fungal growth in the ducts as well - though generally only if you have a humidity problem, or if the coil is gunky too - if the coil is cleaned as the suspected source, make sure the tech tells you if he see mold/fungal growth or excessive buildup of gunky dust in the ducts downstream of the coil, which might indicate a need for duct cleaning. Generally, ducts do not need cleaning except for sometimes in areas with a lot of very fine dust like desert or dustbowl areas, and sometimes in prolonged very high humidity areas where the indoor humidty cannot feasibliy be kept below about 50%.

Obviously, if the smell is prevalent in air handler/furnace area in general, then look around for a source - and a Mold Testing and Remediation company would be the normal vendor.

If due to stinky water coming in through foundation then a Basement Waterproofing contractor would be the vendor.

Sometimes can be due to a sump pit gone anaerobic due to very infrequent pump cycling - put in a few gallons of warm water with a couple of capfuls of chlorine bleach to disinfect and cycle the pump, then several gallons at least of plain water to clear out most of the chlorine (because if it sits there in strength it can damage the pump and plastic piping). Some people like me also put some borax powder in the initial mix (the borax powder found in laundry aisle, NOT Boraxo Soap, which is highly abrasive to pumps) as that is an effective antifungal.

Generally, some sniffing around will pretty quickly tell you if the odor is in the air in the general air handler/coil area and just being pulled into the ducts and therefore being evident at the vents, or if the surrounding area smells fine and the smell only occurs when the unit is blowing air, indicating the source is at the coil or in the ducts.

Here are links to a few previous questions with answers about types and sources of odors FYI - the third one has a long list of similar question links:

Answered 3 years ago by LCD



This is Erick in Member Care. Thanks for your interest in Angie's List!

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Answered 3 years ago by Member Services

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