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Gluten Testing the HVAC System

by | Dec 10, 2019

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After completing the Airborne Gluten Test Series #2, I found myself thinking about the results.  In case you haven’t yet seen that post, I did a series of surface tests in various locations throughout my home, looking for evidence that airborne gluten may have settled there.  The results all came back negative, indicating that the test device did not find any gluten.  I performed that test series after I had found evidence of airborne gluten in our kitchen while my wife and I were “de-glutenizing” our home.


No Gluten is Good News!

Initially, that was my reaction to the results of those tests.  But the more I thought about it, the more I wondered if perhaps those tests didn’t tell the whole story.  Specifically, I realized that the reason I got gluten-free results may have been due to the fact that all of the samples were taken from high points in the house.  One test was taken from the top of a door casing.  The second one was taken from the top of the medicine cabinet in a bathroom.  And the last one was taken from a high shelf.  In every case, the sample was taken from above the 6-foot level.

Of course this choice was intentional.  Those are areas that get cleaned much less frequently, so they collect a lot of dust.  So my hypothesis was that if gluten were circulating throughout the house, it would accumulate more in those areas than in others.  However, after some thought, I realized that this hypothesis relies on the assumption that airborne gluten actually makes it to that altitude.  But what if it doesn’t? 


Gluten Can Fly… But How far?

In most cases, I’d suspect that airborne gluten originates from some powdery gluten-containing substance, such as flour or a baking mix.  Sometimes, when manipulating those substances, such as by pouring them from one container into another, or by mixing them, some of the powder can be ejected into the air.  When this happens, I could envision some of that expelled powder rising to a relatively high altitude in the immediate area.  It obviously had risen to the 5½ foot level when I found gluten on top of our fridge, as detailed in my post for Airborne Gluten Test #1.  But the question is how far can it travel while maintaining that high altitude?  My guess is not far.  By the time it travels 20 feet away, I suspect it will have succumbed significantly to the effects of gravity.

The more I considered this, the more it made sense that this could be the reason why I didn’t find gluten in any of the locations I tested in the Airborne Gluten Test Series #2.  When I did those tests, the nearest one to the kitchen was 20 feet away and 6½ feet high.  My suspicion is that any airborne gluten that had traveled that far would no longer be floating at 6½ feet.

So, I started trying to think of low-lying locations where dust tends to collect.  It didn’t take long to come up with a great candidate for a test:


The HVAC System

I decided the Heating, Ventilation, and Air Conditioning system in our home would be a great test candidate for further examining the phenomenon of airborne gluten.  Our home uses a central air system, whereby air is drawn into a duct called a return duct.  In our case, the return duct utilizes three vents.  Two of those are about 24 inches square, and are mounted vertically in a wall. One sits about a foot above the floor, and the other, about six feet above the floor.  The third return air vent is located in the basement ceiling.

Once air is drawn into the return duct, it is then passed through a filter in order to remove the dust.  After passing through the filter, it is transferred to the HVAC unit, where it is either heated or cooled.  It is then expelled back into the home through a series of vents called registers.  These registers are generally around 12 inches long by 4 or 5 inches wide, and are located throughout the house.  On the main level, they are in the floors, and in the basement, they are located in the ceiling.

There are several reasons why I decided the HVAC system would be a good candidate for this test:

  • Dust tends to collect significantly on the fins of the return air vents.  However, those vents are an area that we usually overlook when cleaning.  If airborne gluten is entering the system, there’s a good chance that some of it might be getting caught up in the dust that sticks to the vents.
  • Because air is pulled into the system through the return air ducts, and then forced out throughout the house via the registers, it makes sense that it would cause most of the air in the home (along with any gluten that might be in that air) to circulate.  It would also likely result in most of the household air passing through the HVAC system many times each day.
  • Since one of the return air vents is near floor level, taking a sample from that vent should address my theory that perhaps gluten may not get high enough to settle on high surfaces.
  • Finally, the biggest factor making the HVAC system a good test candidate is its potential for possibly circulating airborne gluten throughout the home, far from where it actually originated.


Test Synopsis

For this test series, I decided to start by testing the dust that had accumulated on the return air vents.  Initially, I considered also testing dust from the surface of the filter.  That would have been a great idea, were it not for the fact that I had just cleaned the filter only a few days prior.  Finally, I thought I would test dust from the register vents, where the air is blown back into the living space.  While the register vents get cleaned even less frequently than the return air vents, they collect much less dust.  This is probably due to the fact that the air passing through them has already passed through the filter, which would remove most of that dust.

Main Level HVAC Return Air Vents

The return air vent on the main level of our home is about 50 feet from the kitchen.  For gluten to arrive there from the kitchen would require drifting through the dining room for about 25 feet, making a 90 degree right turn, and finally drifting another 25 feet down a wide hallway to the vent.

To perform this test, I used the cotton swab method that I used in previous airborne gluten tests.  I used the swab to pick up gluten from the surfaces of vent fins.  I did all of this while the HVAC unit was turned off, in order to ensure that the dust remained on the swab, rather than getting sucked into the return duct.  As part of the collection of the sample, I collected dust from both return vents in this location.

After the collection of the sample, I cut off the tip of the swab using a pair of side-cutters.  I used the same side-cutters that I used in previous tests, so I made certain to wash them thoroughly prior to their use.  After removing the tip from the swab, I placed it into a new Nima capsule.  After installing the cap, the capsule was placed into the Nima Sensor.


An extremely interesting result!  I can’t think of any reasonable way that gluten would have been able to adhere to these vents if it were not airborne.  Consider, for a moment, the implications of this!  If gluten is entering the return air duct for the HVAC system, it’s going to follow the path in which the air is following which means that it could be getting spread all over the house!  The only impediment to this would be the filter that is installed in the path between the return air duct and the rest of the system.  Is that filter enough to stop the gluten?

Basement HVAC Return Air Vent

The basement return air vent is mounted in the ceiling, approximately 65 feet from the kitchen, where any airborne gluten likely would originate.  In the course of that 65 feet, the gluten would have to make a 90 degree right turn, descend into the basement via the stairwell, and then make another 90 degree turn before getting sucked into the vent.

As I suspected, the basement return vent was quite dusty.  Improving it’s potential gluten-catching abilities was the existence of a few cobwebs.  As before, I used a new cotton swab, running it along several of the fins.

After picking up a substantial amount of dust from the vent, I once again cut off the tip of the swab with a pair of side-cutters.  The cutters were meticulously washed prior to the test.  I then dropped the swab tip into the well of a new Nima capsule.  After replacing the lid, I inserted the capsule into the Nima Sensor, and started the test.


Again, a very intriguing result!  One noteworthy fact in this test is that this vent is in an 8-foot ceiling.  In other words, the high positioning of the vent apparently wasn’t a factor in this case, as opposed to what we saw in Airborne Gluten Test Series #2.  This is likely because of the fact that the air around the vent has suction applied to it whenever the HVAC unit is on.  This suction appears to have overcome gravity’s propensity to pull the gluten toward the floor.  Once again, the implications are obvious.  If gluten is getting pulled into an HVAC unit, it could potentially spread around the home.

Main Level Living Room HVAC Register

Wooden HVAC register vent in a hardwood floor

The first of the registers I tested was one in our living room.  This register had some dust in it, but not much, as compared to the return air vents.  This would stand to reason, since the air must pass through a filter on its way through the HVAC system.

For this test, I removed the register from the floor, and turned it over to expose the side that faces into the ductwork.  Once again, I used a cotton swab, to lift the dust from the surfaces.

After swabbing the register, I used the side-cutters to cut off the tip of the swab, which I then dropped into the well of the Nima Capsule.  I then placed the capsule into the Nima Sensor.


This is a very significant result!  It implies that gluten is probably circulating all the way through the HVAC system, somehow bypassing the filter, and blowing back into the living space through the registers… ALL OVER THE ENTIRE HOUSE.  Now I suppose there’s the possibility that someone may have been standing over that register eating Oreos one day, dropping crumbs into it.  But I think the odds are much greater that airborne gluten is circulating through the system.  Not a good scenario.  The other big question here is “what about the filter?”  Where was it while gluten was passing all the way through the system?  While I can’t really answer that with certainty, I do have a couple of theories.  1) Maybe this filter is not capable of filtering gluten.  It’s a washable filter, the idea being that you don’t have to replace the filter every time it gets dirty.  Perhaps it’s not capable of filtering out very fine particles.  2) Filters don’t necessarily make an airtight seal in the cavity—at least not in our HVAC unit.  In our case, it’s not really even close to a tight seal.  This means that some particulates may be able to get around the filters and flow through the system.

Main Level Bathroom HVAC Register

After testing the living room register, I moved on to one of the bathroom registers.  This register is in the same bathroom where I tested the top of the medicine cabinet in the Airborne Gluten Series Test #2.  That test indicated that there was no gluten present.

As I did in the previous test, I removed the register from the floor, and used a cotton swab to pull dust from the surfaces that normally face into the ductwork.

Again, side-cutters (after having been washed) were used to remove the tip of the swab.  The tip was then placed in to a Nima Capsule, which was then placed into the Nima Sensor.


Once again, a significant result.  While the implications remain the same as in the previous test, this adds to the likelihood that our HVAC system has been happily spreading gluten around our home for years.  I simply can’t buy the theory that someone has been standing over both registers eating Oreos.


After seeing the results of this test series, I can’t help but question how many other households out there have this same issue, but are oblivious, as we were.  I’m all the more convinced now that having gluten-sensitive individuals residing in the same household where gluten-containing meals are prepared and served should probably be a big no-no.  While I think it might be possible if everyone living in such a house were extremely meticulous at washing dishes, surfaces, and hands, this adds a whole new dimension to it.  If gluten can get airborne and then circulate through the house, how in the world do you protect yourself?

It’s one more reason why I’m glad that we de-glutenized our home.  We no longer have gluten in our kitchen, meaning no more gluten-containing flours or baking mixes.  I can live at peace knowing that my gluten sensitive wife and daughter are not being poisoned by uncontrolled airborne gluten.


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