How to find & cure odors that are suspected to come from aluminum building materials or HVAC system components.

This article series discusses common odor sources, including indoor metallic or plastic odors or chemical smells observed at some installations of vinyl exterior building siding or in other plastic or vinyl building products such as windows and trim.

We provide links to articles detailing possible health effects of exposure to indoor VOCs and plastic odors and smells.

Guide to Aluminum-Related Odors In Buildings

A number of readers have asked about the role of aluminum in or on buildings or the use of aluminum evaporator coils in air conditioning and heat pump air handlers as an odor source.

We discuss aluminum siding, windows, and other building components, with a special interest in odors traced to siding, windows, or HVAC coils made of aluminum.

Photo: a very dirty cooling coil in an air conditioning air handler can host mold, bacteria, and other odor-causing biological growth.

[Click to enlarge any image]

In fact, a variety of common building products, coatings, and furnishings may exude odors that disturb at least some occupants, but clean aluminum itself isn't likely to be the culprit.

Most of these "aluminum odor" complaints are traced either to coating on aluminum products or contaminants on those surfaces.

But odor sources in buildings can be tricky to track down.

We provide some suggestions for tracking down these odor sources in buildings, and we offer suggestions for removing or curing these odors.

Aluminum siding, window or screen odors:

We've investigated a number of reports of strange odors in residential buildings that were ultimately traced to vinyl or plastic coatings on windows or siding or trim and that were outgassing.

On new materials, usually these odors dissipate within months of new construction or new installation.

A key diagnostic step in finding odor source was the observation that the odors were strongest when the material under investigation was exposed to sunlight or other sources of heat.

Some Common Aluminum Products that May Have a Role in Odors

• Aluminum air conditioner or heat pump evaporator or "cooling" coils
  
  in the air handler, especially when contaminated with house dust and biological growth - (see photo above on this page)
  
  See details
  
  at at DIRTY HVAC COIL CLEANING PROCEDURES

• Aluminum foil covered building insulation products - (see photo above)
  
  mold or other contamination in the insulation itself may be an odor source, especially if the insulation has been wet

• Aluminum HVAC ducts - (photo above)
  
  may host biological contaminants such as mold, especially if the duct interior or air handler interior have been wet; try having the ductwork cleaned by a professional and double-check that there are no water leaks into the duct system
  
  See WET CORRODED DUCT WORK
• Aluminum siding or trim or window paints or coatings  
  
  in certain product batches by some manufacturers may exude a plastic odor, especially when new or when exposed to heat or sunlight.
  
  See also
  
  PLASTIC ODORS-SCREENS, SIDING.
• Chemical cleaners used on aluminum surfaces
  
  can result in odor offgassing.
  
  Watch out: Don't use acidic cleaners on aluminum HVAC coils. You may corrode the coil, leading to refrigerant leaks and a need for costly replacement of the evaporator coil .
  
  An example, using hydrogen peroxide to clean an AC Cooling coil is given
  
  at the same DIRTY COIL CLEANING PROCEDURES article cited just above.
• Window or door screens
  
  sometimes smell, especially when new or when heated. But if your are sure that your window or door screen is aluminum and you identify it as an odor source, you should first try cleaning the screen - else replace it.

Aluminum-Odor Diagnosis Strategies:

You can start tracking down the cause or source of an odor in one or more of several ways:

1. ODOR DIAGNOSIS SIX STEPS - taking an orderly approach to odor source tracking
2. ODOR DIAGNOSIS CHECKLIST - an easy checklist of stuff to examine or test
3. ODORS GASES SMELLS, DIAGNOSIS & CURE - includes a catalog of places to look when tracking down an odor source
4. SMELL PATCH TEST to FIND ODOR SOURCE - procedure for testing specific surfaces or items to see if an odor source of if they have absorbed and are re-emitting an odor

Research on Aluminum Building Component or HVAC Coil Off-Gassing & Odors in Buildings

• Bjorkroth, M., O. Seppanen, and A. Torkki. "Components of the air handling unit and air quality." In Proceedings of Healthy Buildings, vol. 97, no. 1, pp. 599-603. 1997.
• Fromme, H., A. Mattulat, T. Lahrz, and H. Rüden. "Occurrence of organotin compounds in house dust in Berlin (Germany)." Chemosphere 58, no. 10 (2005): 1377-1383.
• Hipchen, John C., Annina Hogan, and Dale Powell. "Comparison Study of Bio-Growth in Commercial AHU’s Using Copper Heat Exchangers and Components." (2018).
• Kerka, William F., and Elmer R. Kaiser. AN EVALUATION OF ENVIRONMENTAL ODORS [PDF]ournal of the Air Pollution Control Association 7, no. 4 (1958): 297-301.
• Peng, Chiung-Yu, Cheng-Hang Lan, and Tzong-Jer Wu. "Investigation of indoor chemical pollutants and perceived odor in an area with complaints of unpleasant odors." Building and Environment 44, no. 10 (2009): 2106-2113.
• Schmidt, Michael G., Hubert H. Attaway, Silva Terzieva, Anna Marshall, Lisa L. Steed, Deborah Salzberg, Hameed A. Hamoodi, Jamil A. Khan, Charles E. Feigley, and Harold Michels. "Characterization and control of the microbial community affiliated with copper or aluminum heat exchangers of HVAC systems." Current microbiology 65, no. 2 (2012): 141-149.
• Siegel, Jeffrey, and Ian Walker. DEPOSITION OF BIOLOGICAL AEROSOLS ON HVAC HEAT EXCHANGERS [PDF] No. LBNL-47669. Lawrence Berkeley National Lab.(LBNL), Berkeley, CA (United States), 2001.

Field Reports: Sources of & Cures for Aluminum-Related Odors In or Around Buildings

On 2022-11-15 by InspectApedia (Editor) (mod) - aluminum itself does not smell but it may host smelly contaminants especially on an HVAC coil

@Richard,

Thanks for the added comment. So actually we agree. Aluminum itself, such as that used as fins or fins and tubing on a HVAC coil, does not emit a noticeable odor, but certainly contaminants that collect on the coil can smell horribly (and may corrode the aluminum as well).

The smell is from the contaminants, not the metal.

In HVAC systems there have been decades of research on these problems, including experiments with making heat exchangers or HVAC coils intended to resist microbial growth. Coils in particular are exposed to dampness or even water from condensation that, combined with the naturally-occurring microbials in house dust (skin cells, bacteria, mold) are at risk of becoming a fertile breeding ground and smell source.

But do not blame the aluminum coil. In fact for decades it's been known that aluminum is one of the more odor-resistant metals for use in HVAC systems. (Kerka 1958)

Supporting research is given above on this page.

On 2022-11-13 by Richard

@danjoefriedman, You say that aluminum will not smell I hate to contradict you recently had a train air-conditioning unit giving off a horrible smell cleaned several times turned out it was the aluminum coil growing bacteria so aluminum will not smell but it’s a great breeding ground for bacteria that does train under warranty

Apoxsee coated the coil no more problem

On 2022-06-21 by InspectApedia (mod) - Try a smell test: where, really, is the odor coming-from?

@Kalyn,

Try a smell test: where, really, is the odor coming-from?

Fan cage or enclosure
Fan blades
Fan wiring
Fan motor
somewhere else.

We'd use different approaches for different fan parts.

Watch out: wetting or scrubbing an electric fan motor may result in damage to internal insulation parts in the motor such as insulation on motor windings. If you've done that the motor is destroyed.

On 2022-06-21 by Kalyn - dirty fan gives off B.O. Smell

My friend gave me an expandable window double fan he has had well over 10 years. it was caked with dirt and grim but I pulled it in to see if it works.

The overwhelming smell of strong body oder almost knocked me out. I've taken the fan apart and there is a off white greyish crusty material by the wiring and around the sides of entire fan.

Including the air slots on both sides. I've sprayed, scrubbed, soaked this thing and it hasn't let up. Not even a little bit .please help cause I'm broke and it's hot outside.

On 2021-02-14 by (mod) - Aluminum is actually not a material that will emit an odor unless ...

Amanda

Aluminum is actually not a material that will emit an odor unless it is from a paint coating or from something it has spilled on the aluminum.

So if there's an odor that's bothering you I would look a little further to see what the possible Source might be such as a new sealant that has been applied somewhere or even an animal that has crawled into an opening or died somewhere nearby.

On 2021-02-14 by Amanda - chemical odor from old aluminum sliding doors

We have old aluminum sliding doors and they are emanating a slight chemical smell. Especially on hot days. Is this something I should be worried about? Is it harmful?

Thank you

On 2020-10-02 by Anonymous - we cleaned our coil and ducts but they smell

Thank you. Just to be clear, on all inspections of our HVAC system, including the one we had this week, we've been told our system is not only clean, but incredibly clean: the coils, the fan, etc, everything.

And, as noted, we had the ducts cleaned a little less than 2 yrs ago and were told they were quite clean at the get go. Knowing that, would you change or re-prioritize your recommendation.

On 2020-10-02 - by (mod) -

Take a look at DIRTY HVAC COIL CLEANING PROCEDURES

and you'll find a detailed discussion of using, buying and sources of A/C coil cleaners.

On 2020-10-02 by Anonymous - what cleaning product should we use to clean our aluminum coil in the air handler?

Thank you, Dan. Do you have a cleaning product you recommend (or suggest avoiding) to clean the coils, air handler, and blower?

And how long does that product tend to linger in the air after use? (I assume the smell will get dispersed throughout the house and I'm very sensitive to VOC's.)

We use a really good media filter and change it frequently, but will do so now. And we'll have our ducts inspected as per your suggestion. (We had them cleaned when we bought the house a couple of yrs ago and they were in very good shape at that time, but that was before we bought the new A/C and started having this problem so that's kind of moot.)

As far as a more thorough inspection of the air handler and ductwork, would you suggest using a duct cleaning company (we have a very reputable resource for that) or should we involve a mold inspector to coordinate w/a duct cleaning company and/or the HVAC technician?

On 2020-10-02 - by (mod) - Locker room smell is mold, not aluminum oxide

Best would be to have a more thorough inspection of the air handler and ductwork;

It seems odd to me that switching between A/C and Heat would produce and odor that we could trace to "dust on the coils" because the system's air flow is passing through the coil (condensing coil or cooling coil) whenever the blower operates.

I agree that moisture on the coil or elsewhere in the system will be greater when in cooling mode and that may, in turn, be producing or stimulating mold contamination;

I've not found an authority that says aluminum oxide smells like a locker room; but there are some molds that are so characterized.

Have the coil cleaned and the air handler and the blower fan itself cleaned; install a fresh air filter; inspect ALL of the ductwork;

Watch out: there are indeed some indoor mold contaminants that smell like "sweaty gym socks".

On 2020-10-01 by Anonymous - oxidation on aluminum HVAC coil smells like damp cardboard or a sweaty locker room

For the second year in a row at this time of year during the season transition when we switch back and forth btwn A/C, nothing, and heat, the A/C smells when it comes on after it’s been off for a day or so.

To me it smells like a sweaty locker room, most others say it smells like damp cardboard. The smell is immediate and throughout the house rather than local to any one register/duct.

Last year our HVAC people couldn’t figure out the source, nor could our IAQ person. Of note, the A/C is new (purchased 2 yrs ago – new coils and compressor).

When starting the A/C up again after the winter, the smell is not there so we assume that whatever is causing it has dried out from the heat running.

This week, an HVAC tech came out to do the seasonal check and said the source of the smell was “dust” on the coils and in the pan. He pointed to white flakey discolorations, particularly at the joints of the coils. I asked if it was mold and he said no, while acknowledging he’s not a mold expert.

My husband recalls the tech also said the dust isn’t from the environment that got stuck on the coils and drain pan as a result of air flowing through the system, but rather that it’s actually aluminum oxide (the tech didn’t call it that specifically) that was the result of an interaction between a new/fresh aluminum surface and moisture.

The tech said he often sees this on recently installed systems and that it stabilizes over time. He identified the dust/oxide as the potential source of the odor when it becomes wet. He pointed out where it had built up on the tubes interconnecting the coils and particularly heavy at the joints where there was solder. There was also quite a bit of the white, flaky material in the channels that drain the pan.

My husband researched aluminum oxide and the whole story makes chemical sense to him, the weakest point being the hypothesis that it is the origin of the smell. But it could be.

Our questions for you are:

(1) Does this sound like a reasonable explanation for the odor?

(2) From the photo I’m attaching, can you tell if the stuff is metallic oxide (crystalline) or something else, like mold?

On 2013-01-29 by (mod) - smell coming off windows made of aluminum and glass.

Rema

Sorry to say that your town government is not likely to offer help in tracking down the cause and recommending a cure for odors blamed on aluminum storm windows.

You will want to find a local environmental test consultant or possibly even an experienced home inspector to help you understand the odor problem and recommend a cure.

See CONSULTANTS & EXPERTS DIRECTORIES

On 2013-01-29 by Rema Smith, rema.smith@cox.net - plastic smell coming off our storm windows made of aluminum and glass.

Please let me know who I can contact in my town government to help us figure out the plastic smell coming off our storm windows made of aluminum and glass.

There is no plastic or vinyl in them.

...

Continue reading at ODORS in AIR HANDLERS & DUCT WORK or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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• ODORS GASES SMELLS, DIAGNOSIS & CURE - home
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  • VINYL SIDING or WINDOW PLASTIC ODORS
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• SMELL PATCH TEST to FIND ODOR SOURCE
• WINDOW OFFGASSING ODOR COMPLAINTS, FIBERGLASS & VINYL

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