Part Deuce: Do activated-carbon garments really work?

Part I: Do activated-carbon garments really work?
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Due to the incredible amount of response — both positive and negative — that I received on my article “Do Activated-Carbon Scent Elimination Garments Really Work?” I felt compelled to write more on the topic.

In that article, I provided a scientific basis to substantiate my claim that the use of activated carbon (AC) in garments to eliminate or reduce human odor is a poor application.  Consolidating a mountain of detailed information into a short, readable article was both difficult and challenging … I could have easily written a book on the subject.

Knowing full well when I finalized the article, although accurate in content, there was much detail missing; I was sure that it may be “picked apart” by the manufacturers of AC clothing.

Indeed, it was picked at, but the positive support for the article was far greater than the negative.

My objective when I wrote the article was to simply educate bowhunters.  I wanted to give them a straightforward non-marketing based perspective.  I am not affiliated with any competitors of these scent-elimination clothing manufacturers, I’m not trying to sell anything, nor do I have a grudge. I believe I reached most folks who had an open mind on the subject and/or those who already had some suspicions.  

The reactivation potential of activated carbon was the biggest point of contention.  Representatives from two AC-clothing manufacturers indicated to me that the word “reactivation” was a term that is used loosely.  In short, the term “reactivation” means to “totally” (100 percent) recharge the adsorption capacity of activated carbon. 

It also was told to me that indeed the activated carbon in these garments isn’t totally reactivated after the first use, but rather partially “regenerated” or partially “desorbed” through exposing the garments to short periods of low heat from a household clothes dryer. Allegedly, the resulting partially reactivated carbon then has enough capacity to adsorb more odors. 

It is true that some desorption of stinky gases will take place when activated carbon is exposed to temperatures below 400–800°C (752-1472°F), but there is a point when the temperature is too low to have any real appreciable desorption effect on activated carbon. 

A Virginia Tech. University web site page indicates that activated carbon can be partially desorbed between temperatures ranging from 100–649°C.  One hundred degrees Celsius (100°C) translates to two hundred and twelve degrees Fahrenheit (212°F).  Keep in mind, this is the extreme low end of the temperature range where partial desorption of stinky gases may occur.  And, I don’t know of any household dryers that have the ability to boil water.  Most clothes dryers peak out at less than 150°F. 

If you would like to view the university web site that I am referring to, you can view it at this web site address: http://www.ce.vt.edu/program_areas/environmental/teach/wtprimer/carbon/sketcarb.html

There are several other principals that I did not mention in my last article that would substantiate my claim. One principal I did mention in my previous article was never refuted by any of the garment manufactures.  That statement follows: 

“Here is something else you should consider before purchasing an activated carbon scent elimination garment:  Activated carbon’s adsorption effectiveness when used in an air filter application becomes greatly reduced when it is wet.  So what happens when you sweat, especially during those early season bow hunts?  Your clothing gets wet of course.  A leading manufacturer of these special garments admits that no laboratory testing has been conducted to determine the effectiveness of the clothing when it is wet from hunter’s perspiration.” 

High humidity and moisture from either sweat, rain, fog or down right humid conditions has the potential to greatly reduce or completely compromise the adsorption effectiveness of activated carbon contained in these garments.  This is irrefutably a scientific fact. 

AC adsorbs many different compounds and one of them is water, both liquid and gaseous forms.  The very first time you don your garment, the AC not only starts adsorbing stinky gases; it also starts adsorbing water vapor that is constantly being released through your skin. 

Take a plastic bag and wrap it tightly around your hand and walk around with it for about ten minutes.  Moisture vapor being released from your skin has nowhere to go and soon you’ll have a hand that is soaking wet.  It is astonishing how much moisture escapes through the skin even when you are not engaged in physical exercise. 

If you out right sweat liquid water (perspiration) and the garment with AC contained within becomes wet, then the adsorption effectiveness of the activated carbon is rendered utterly useless.  Surface tension and capillary action principles will cause the entire AC particle to become totally encapsulated by liquid water droplets, which creates a liquid barrier to other gases, including the stinky ones. 

Unless the stinky gases can come in contact with the AC particles, adsorption will not occur.  It is as simple as that. 

Not so amazingly enough, this basic principal is virtually disregarded in the marketing campaign practiced by the manufacturers of AC garments.  Scent Lok brand clothing produces an eight-paged (front and back) training guide designed to educate hunters on how to use their specialty clothing line.  In the Frequently Asked Questions section of the training guide, and on the company’s web site, one of the questions-and-answers reads verbatim as follows:

Q:   “What happens if it rains when I’m wearing Scent Lok?”

A:   “The water will not affect the adsorptive abilities of the activated carbon.  Scent Lok will work equally well whether it is hot, cold, wet or dry.”

This statement is ludicrous.

This is product marketing at its worst. 

The U.S. Army Corps of Engineers – Engineering and Design, Adsorption Design Guide, Design Guide No. DG1110-1-2, states: “Relative humidity above 50 percent may result in adsorbed and condensed water vapor blocking the pores of the particles and interfering with the diffusion of the contaminants to the adsorption pores.” 

So if you wear this specialty clothing in the field where relative humidity conditions are above 50 percent, or if you sweat, then watch out.  Irregardless what the relative humidity conditions are on the day of your hunt, if you don AC clothing and start walking to your stand, this mild physical exertion will cause your body to release a copious amount of moisture, resulting in, or exceed a relative humidity condition of 50 percent between your skin and the garment.  By the time you reach your stand it is likely the AC contained in the garment will be saturated with water and thus rendered useless. 

Of course, this is assuming AC garments can actually be regenerated in a household dryer. 

The illustration below shows how liquid water blocks the surface area of AC and prevents stinky gasses from coming in contact with it.  

A truly practical application for AC is where it is used to filter a pressurized flow of water or air.  In this application, the filtered media (water or air) is forced through a vessel containing AC. A Britta water filter cartridge is a good example.  You don’t throw a handful of activated carbon into a bucket of water and expect it to adsorb contaminants out of the water.  No, you must force a stream of water through your Britta water filter cartridge with the aid of pressure.  Similarly, you don’t hang your air filter from the ceiling in your living room and expect it to filter stink and dust from the air.  Rather, your air filter is situated in a wall vent and air is drawn through it via negative air pressure from your air conditioning system. 

When your body releases stinky gases, they flow though the air as hitchhikers on a wave of heat, which also is released from your body.  The heat and the stinky hitchhikers obey simple laws of physics and tend to follow the path of least resistance.  The path of least resistance is not through the garment and into the many pores and channels contained in the AC.  The path of least resistance is to go around the garment, through major openings such as your belt line, your collar and sleeves, or through the opening of your facemask.  This is called the “chimney effect.” 

Like smoke rising from a chimney in your home, most of the stinky gasses bypass the garment and expel through the opening of the collar.  Furthermore, even if small amounts of stinky gases manage to permeate through the fabric, the path of least resistance is still to go around the AC particles and through the interstitial spaces (gaps or voids) of the garment’s fibers and eventually into a whitetails nose. 

There are other principles that I didn’t mention in my last article and there are others that I am not mentioning here as well.  Some of the principles would be difficult to convey and interpret. I had several readers tell me that some of the principles in my first article were difficult to understand as it was.

Again, a book could be written on this subject.  When you look at all the different principles cumulatively, it is apparent that this is an extremely poor application for AC.  A screwdriver is a great tool, but it’s not something used to drive nails.

I’ve received several anecdotal scenarios from AC-garment users, whom explained that they were upwind of the biggest buck they had ever seen and the deer never knew they were nearby.  The fact this happened made the hunter a true believer in these garments. 

To those true believers I’ll say this:  Thousands of big bucks have been killed by bowhunters who were up wind of big bucks before AC garments were developed and marketed.  Even if you did harvest a big buck that happened to be down wind of your location, it doesn’t mean the AC garment you were wearing had anything to do with your success. 

As many bowhunters know, in the early morning hours, temperatures begin to climb and thermals will rise and carry your scent straight up and away from whitetail noses.  Additionally, a mindless rut crazed buck will virtually run over a hunter to get to a hot doe.  There are countless other reasons and scenarios that can lead to a deer not smelling a hunter even if the hunter is directly upwind of their quarry.

I want to thank the editor at FastestBows.com for having the guts to publish my first article, when other hardcopy hunting magazines, with the exception of “The Whitetail Fanatic,” wouldn’t touch it.  Hmm … I suspect this is because AC-garment manufacturers heavily advertise with them. 

I guess money really does talk.

I will bring closure to this article with the same words I used to close my first article:

Biologist and environmentalist Michael Corrigan is an avid bow hunter and enjoys educating other bow hunters.

ED NOTE: Though this article does contain scientific merit, the opinions of the author do not necessarily represent the views of this web site.