Scent Lok Activated Carbon Articles - The Science, Not The Hype

Over the last few years several questions have arisen as to whether or not activated carbon clothing suits work as advertised to keep hunters from being detected by deer (that might smell the odors given off by humans, or any unnatural odors associated with the humans while they are hunting). The questions asked include: Is there enough activated carbon in the scent-elimination suits for them to work as the manufacturers claim they do? How long will activated carbon continue to work? Can the suits be re-activated as the manufacturers claim they can be? Are activated carbon suits adversely affected by humidity?

Activated carbon is used as a filter medium because it has an affinity to "volatile organic compounds". When humans perspire they emit volatile organic compounds and other chemicals, such as hydrogen sulfides, which can be trapped by activated carbon. The manufacturers of activated carbon scent-control suits claim their clothing works because the activated carbon (which is glued to or impregnated into the fabric of the clothing) blocks the release of human odors, or "traps" the odors by a chemical bonding process called "adsorption".

Adsorption occurs when activated carbon grabs and holds other compounds, including gases, scents and odors, at the molecular level. The amount of odor that an activated carbon filter medium holds is determined both by the amount of activated carbon in the entire medium and by how thick the layer of activated carbon on the fabric is. In the case of a scent-elimination suit, the carbon layer is very thin, which means there is very little activated carbon in the suit. In fact, the scent elimination suits are so thin that they hold relatively small amounts of activated carbon, and the activated carbon is so widely spaced in some suits that the suits allow air and odors to go through the suit without coming into contact with and being trapped by the small amounts of carbon in the suit.

One of the problems with trapping odors by adsorption is that adsorption continuously occurs, unless the activated carbon is kept in an airtight unscented bag from the moment it is first activated. Since activated carbon will eventually become full of odors, it cannot work any great length of time. If activated carbon clothing is not put into a sealed bag the moment it is activated, and kept that way until it is used for hunting, it will have adsorbed numerous odors. Depending on how thick the layer of activated carbon is in the suit, it may not work to stop human odors the very first time it is used.

In an attempt to bring some legitimacy to their products, the manufacturers of scent-control clothing have acknowledged this to some extent. Many manufacturers recommend that the clothing should be immediately washed, and then "re-activated" by placing the suits in a clothes dryer as soon as they are purchased. However, many activated carbon experts and chemists have questioned the claims by these manufactures, that activated carbon can "totally eliminate all human odors", and that the activated carbon in the clothing can be reactivated, several times with no loss of carbon in the clothing, or in the adsorbtion (of odor) capability of the activated carbon in the clothing, when the clothing is placed in a clothes dryer with temperatures lower than 200 degrees Fahrenheit. The maximum temperature of most household clothes dryers is less than 165 degrees F.

My research about activated carbon, as is used by the manufacturers of activated carbon clothing used for the purpose of reducing human and other odors while hunting, suggests that the claims of Scent Lok and the other manufacturers are highly exaggerated and mis-leading, and may in fact be false.

Is there enough activated carbon in a Scent Lok Suit to Work?

The Columbus Industries Patent Application # 5,678,247 states:

The layer of odor absorbing material (activated carbon) should be at least 1/8 inches thick to provide sufficient activated carbon and very importantly provide a higher residence time of the human scent within the odor absorbing layer to achieve greater odor adsorbing efficiency. It is more preferred to employ a thickness of about 1/4 inches for the odor absorbing sheet layer.

I personally separated the layers of a Scent Lok in August of 2006, to determine how much activated carbon was in the suit. I first noticed that there was not enough activated carbon to cover the entire surface of the fabric, which meant that odors could go through the suit without ever coming into contact with the activated carbon; making the suit ineffective.

The layer of activated carbon in the Scent Lok was less than 1/8 inch, probably more like 1/50 of an inch. But, in its patent, the above company states that there needs to be at least 1/8 inch of activated carbon, and "it is more preferred to employ a thickness of about 1/4 inches" of activated carbon to provide sufficient "odor adsorbing efficiency".

This Patent, which may be for the material Scent Lok uses in its clothing, states, in this US Government document, that there is not enough activated carbon in Scent Lok suits, to work!

Reactivation of Activated Carbon - The Real Science

2007

Note: To set the stage for the following explanation of how the (powdered) activated carbon in a Scent Lok cannot be "reactivated" as Scent Lok representatives claim it can be, we must first define what the terms "reactivation", "desorbtion", "gasification", "volatile materials", "vapors" and "human perspiration odor" mean.

Reactivation

As shown by the above article "reactivation" of activated carbon involves four different processes (drying, desorbtion, pyrolysis, gasification); not just "desorbtion" as it appears Scent Lok refers to when it says that their product can be "reactivated" in a household dryer (which generally produce maximum temperatures between 150 and 180 degrees F.

Gasification

The web site at http://www.ciwmb.ca.gov/organics/Conversion/Gasification/ states:

Gasification is a process that uses heat, pressure, and steam to convert materials directly into a gas composed primarily of carbon monoxide and hydrogen.

Gasification technologies differ in many aspects but rely on four key engineering factors:

Gasification reactor atmosphere (level of oxygen or air content).

Reactor design.

Internal and external heating.

Operating temperature.

Typical raw materials used in gasification are coal, petroleum-based materials, and organic materials. The feedstock is prepared and fed, in either dry or slurried form, into a sealed reactor chamber called a gasifier. The feedstock is subjected to high heat, pressure, and either an oxygen-rich or oxygen-starved environment within the gasifier. Most commercial gasification technologies do not use oxygen. All require an energy source to generate heat and begin processing.

There are three primary products from gasification:

Hydrocarbon gases (also called syngas).

Hydrocarbon liquids (oils).

Char (carbon black and ash).

It is during this "gasification" process that "vapors" (some of the compounds of human perspiration odors) are "driven out of the pores" of activated carbon.

Volatile Materials

The United States EPA (Environmental Protection Agency) web site at http://www.epa.gov/iaq/voc.html states:

Organic Gases (Volatile Organic Compounds - VOCs)

Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide array of products numbering in the thousands. Examples include: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions.

Organic chemicals are widely used as ingredients in household products. Paints, varnishes, and wax all contain organic solvents, as do many cleaning, disinfecting, cosmetic, degreasing, and hobby products. Fuels are made up of organic chemicals. All of these products can release organic compounds while you are using them, and, to some degree, when they are stored.

EPA's Total Exposure Assessment Methodology (TEAM) studies found levels of about a dozen common organic pollutants to be 2 to 5 times higher inside homes than outside, regardless of whether the homes were located in rural or highly industrial areas. Additional TEAM studies indicate that while people are using products containing organic chemicals, they can expose themselves and others to very high pollutant levels, and elevated concentrations can persist in the air long after the activity is completed.

Volatiles, are substances that can be "desorbed", which may include some components of "human perspiration odor"; but, not but not all of them can be "desorbed".

Vapor

Wikepedia defines vapor as:

Vapor or vapour (see spelling differences) is some matter in gaseous state, while being normally a solid or liquid at room temperature.

Although vapor and gas are frequently (incorrectly) used interchangeably, vapor refers to a gas phase in a state of equilibrium with identical matter in a liquid or solid state below its boiling point, or at least capable of forming solid or liquid at the temperature of the vapor. The term gas refers to a compressible fluid phase, as in common usage. Fixed gases are gases for which no liquid or solid can form at the temperature of the gas (such as air at standard temperature). A liquid or solid does not have to boil to release a vapor. The atmospheric boiling point of a liquid is the temperature at which the vapor pressure is equal to one atmosphere (unit). See the entry on vapor pressure for more information on this topic.

The vapor pressure is the equilibrium pressure from a liquid (or solid) at a specific temperature. The vapor pressure of a liquid or solid (pure or a mixture) is not affected by the pressure in contact with the liquid or solid.

Odor

Wikepedia defines odor (as in human perspiration odor) as:

An odor or odour (see spelling differences) is a chemical dissolved in air, generally at a very low concentration, which we perceive by the sense of olfaction. Odors are also called smells, which can refer to both pleasant and unpleasant odors. In contrast, stench and stink are used specifically to describe an unpleasant odor. The terms fragrance, scent, or aroma are used primarily by the food and cosmetic industry to describe a pleasant odor, and is sometimes used to refer to perfumes.

Human perspiration odor is a gas or vapor, which contains substances such as uric acid, leucine, valine and lactic acid, that may partially be "driven out of (the) pores" of activated carbon during the "desorbtion" stage of reactivation of activated carbon.

Conclusions: The above article states that "desorption" (which Scent Lok refers to as "re-activation") of GAC (granulated activated carbon) occurs between 100-649 degrees C (above 212 degrees F). This is when volatile materials (those solids that easily turn into gas) are driven off. This clearly is not how any form of activated carbon can be reactivated, because human perspiration odor is not solely a "volatile organic compound".

The article goes on to state that "gasification" (using temeratures between 649-1038 degrees C) of "vapors" and residues (airborne gases and scents such as some of the compounds of human perspiration odor) from the previous stages of the "reactivation process" are "driven out of pores" of granulated activated carbon.

The article clearly shows that the minimal amount of activated carbon (which does not even cover the entire surface of the fabric used in a Scent Lok suit), cannot be reactivated (when it comes to human perspiration odors) in a household dryer, because household dryers rarely produce temperatures in excess of 150-180 degrees. It clearly states that vapors (human perspiration odors) are not driven off (desorbed or re-activated from activate carbon) until activated carbon is raised to 649 C (1200 degrees F). Very few hunters have access to such a dryer.

This information suggests that Scent Lok may be engaged in false if not deceptive advertising. In fact "re-activation" is the basis for Scent Lok's claim that their suits are effective because they can be "reactivated" and can therefore be used for an indefinite period of time; which research shows cannot be done.

The Following article is from the NORIT Activated Carbon web site. Note that it is about activated carbon used for air; not only water.

NORIT's reactivation service is a cost-effective and environmentally sound solution. 'The recent implementation of the EU Landfill Directive in the UK is further boosting interest in thermal reactivation of exhausted GAC,' comments Mark Currier, NORIT UK Sales Manager. During thermal reactivation, the exhausted granular activated carbon (GAC) is heat treated in dedicated kilns at temperatures exceeding 900 C. Adsorbed organic compounds are cracked and oxidised. Following reactivation, the GAC's adsorptive properties are restored to a level comparable to that of virgin GAC. As a result, the GAC can be reused in the same or a similar application.

Exhausted carbon: green and amber;

The relevant EU regulation categorises exhausted GAC as either green (used in water purification and food production) or amber (used in the treatment of gas/air or wastewater). NORIT reactivates green and amber GAC in completely separate systems, precluding the risk of cross contamination.

The above article shows that activated carbon for air is reactivated (de-sorbed) at temperatures above 900 degrees C. Again, no hunter has access to such a dryer, and if he did, it would incinerate his suit.

The following quote is from the CPL Carbon Link web site at http://www.activated-carbon.com/5-1.html

Reactivation restores the activated carbon to a state where it is virtually identical to the properties of the virgin pre-cursor. This is done by undergoing the process of activation a second time rather than simply displacing adsorbed organic material by processing at high temperature. The organic compounds removed from the spent adsorbent are passed through a sophisticated multi-stage treatment system ensuring the reactivation system does not cause pollution while undertaking a recycling operation.

The above article states that "reactivation" to the state of the virgin precursor occurs after both high temperature has been used to "desorb" the carbon, and then it has to be reactivated "a second time". It appears that "reactivation" (which is the term used by Scent Lok) is even more difficult than desorbtion. And it is unlikely any hunter has access to a facility to reactivate their suit; or the money to do it.

The following quote is from the Chemviron Carbon web site at http://www.chemvironcarbon.com/cci/introcci.htmhttp://www.chemvironcarbon.com/cci/introcci.htm

Activated Carbon Cloth (ACC) was originally developed by the British Ministry of Defence for use in chemical warfare suits. Since the early 1970's Charcoal Cloth International (CCI) a subsidiary of Chemviron Carbon has been developing and manufacturing ACC under the ZORFLEX^® brand name for a wide range of demanding markets.

The above article shows that activated carbon cloth (used in hunting suits) was used for a variety of purposes as early as the 1970's, which shows that the use or application of activated carbon began much earlier than the non-patent of Scent Lok for the same use or application in the early 1990's. Their patent is invalid; as it stands, they had no right to sue anyone, threaten to sue anyone, require royalties from anyone, or stop anyone from selling activated carbon suits.

The following article is from the Inist web site at http://cat.inist.fr/?aModele=afficheN&cpsidt=16558801

Bench-scale experiments investigated the effect of electrolyte mixing on the effectiveness of an electrochemical reactor for the reactivation of granular activated carbon (GAC). Two different GACs (F-400 and WV-B) were loaded with phenol via batch adsorption tests, then electrochemically reactivated and finally reloaded with phenol. Reactivation was conducted in a recirculating flow reactor with a 0.1 M NaCl solution as the electrolyte. Cathodic reactivation was more efficient than the anodic reactivation and increasing the degree of electrolyte mixing decreased the cathodic reactivation efficiencies, while there was no significant change in the anodic reactivation efficiencies. Higher degrees of electrolyte mixing decreased the local pH at the cathode and consequently reduced the desorption driving force and therefore reduced the reactivation efficiency. The electrolyte mixing lowered the cell voltage. However, this advantage was overshadowed by the increased energy consumption required for the electrolyte pumping, the reduction of the oxidation rate of phenol, and a 20% reduction in the reactivation efficiencies. Thus, electrolyte mixing of the electrolyte is not recommended in the electrochemical reactivation of GAC.

Note that this method includes "electrochemical reactivation", which no hunter I know of has access to.

The following article is from the Cameron carbon web site at http://www.cameroncarbon.com/spent_carbon.html

Cameron Carbon offers spent activated carbon reactivation (recycling) services at a fully permitted reactivation facility. Spent carbon is recycled in specially designed high temperature furnaces that can restore the carbon's pore structure to new or near new quality. The organics that are vaporized from the spent carbon are fully destroyed downstream of the furnace by an air pollution control system. Certification of VOC (volatile organic compounds) destruction can be provided upon request.

The above article states that "reactivation" (the word Scent Lok uses) occurs when activated carbon is placed in "specially designed high temperature furnaces", and ONLY THEN is it restored to new or nearly new quality. NO hunter I know of has access to such a facility.

The following article is from the CMCC-AC web site at http://www.cmcc-ac.co.jp/english/product/catalog1.html

Activated carbon that has dropped its adsorbing capability can be recovered in its performance by the reactivation process and can be used in the adsorption process again. When activated carbon adsorbs impurities, a balanced relationship of adsorption is established among the adsorbate (i.e. substance adsorbed by activated carbon), activated carbon, and medium (i.e. substance surrounding the adsorbate and activated carbon such as water or gas).

Reactivating means that this balanced relationship of adsorption is changed and adsorbate is separated from activated carbon. Depending on the reaction mechanism, there are 6 types of reactivation; decompression reactivation, heating and leaving reactivation, chemical reactivation, solvent reactivation, substitutive reactivation, and oxidation and decomposition reactivation.

I don't know of any hunter who has access to 5 of the reactivation types, and we have already established that even partial reactivation, or "desorbption" as it is called, must occur at temperatures over 212 degrees F.

The following article is from the Siemens web site at http://www.usfilter.com/en/Corporate/Technologies/activated_carbon_regeneration_technologies?OverrideChannel=%2FChannels%2Fen%2FCorporate%2F

Our carbon reactivation facilities process RCRA hazardous and non-hazardous liquid and vapor phase spent carbons. After inspection and acceptance, the spent carbon is heated to 1600°F to ensure proper reactivation. The cooled reactivated carbon is identified by lot numbers. Each carbon lot is sampled and analyzed in accordance with Westates' QA/QC program. This process assures you receive the highest quality reactivated carbon. The entire process is computer controlled and monitored, ensuring the facility meets or exceeds federal and state regulatory requirements for air and water discharges. A "Certificate of Reactivation" can be issued for each shipment of recycled carbon. This certifies that the spent carbon has been recycled in a manner that meets or exceeds all applicable RCRA and Benzene NESHAP regulations.

I don't know of any hunter who has a 1600 degree dryer.

I personally spoke to a Chemist at 3M here in St. Paul, MN. He told me that due to the length of the human perspiration odor it would be impossible to desorb and gasify it (release human perspiration odors / smells) from activated carbon at temperatures below not 1200 degress F. 1200 degrees F, can anyone say "Incineration"?

The following article is from the FreePatentsOnline web site at http://freepatentsonline.com/6423657.html

United States Patent 6423657

Abstract:

"A process and a set of equipment for reactivating spent activated carbon onto which pollutants were adsorbed. The present process comprises subjecting the activated carbon to be reactivated in a mixed solution consisting of ethanol, sodium hydroxide solution and water to effectuate the desorption of the pollutants adsorbed on the activated carbon. The equipment includes (A) a mixing tank for mixing given amounts of water, ethanol and sodium hydroxide solution which are supplied from the respective receptacles thereof; (B) a reactivation reactor for receiving the mixed solution from the mixing tank and subjecting the spent activated carbon filled therein to the mixed solution to effect the desorption of the pollutants adsorbed on the spent activated carbon, wherein the reactivation reactor includes a unit for regulating temperature of the mixed solution; and (C) a storage tank for receiving the reactivated carbon."

Does any hunter have access to this means of reactivation?

Scent Lok Licensing Agreements

2008

In the early 1990's Scent-Lok applied for and received a patent on the use of activated carbon for several different applications and/or articles of clothing used in conjunction with the control, reduction or elimination of scents, including human related or human produced odors, while hunting. Since the granting of that patent Scent-Lok has done what any company holding a patent does; they have aggressively protected the patent, warning several companies not to produce clothing meant to control, reduce or eliminate unwanted odors while hunting, whether the clothing contained activated carbon or not.

Is the Scent-Lok Patent Valid?

By T.R. Michels

2007

Recently some questions have arisen as to whether or not the Scent-Lok Patent is valid. On May 11, 2005, the United States Patent and Trademark Office mailed a document to Scent-Lok, notifying them that "Claims 1-10" of their patent were temporarily "subject to reexamination" and were temporarily "rejected". According to the document, Scent-Lok had until July 11, 2005 to respond to this document. Failure by Scent-Lok to respond "will result in termination of the process and issuance of an ex parte reexamination certificate in accordance with this action."

The document cites "Popper" and "Floyd" as previous patent holders and may imply that Claims 1-10 of the Scent-Lok patent are invalid, because either Popper or Floyd covers the claims under previous use. Previous use of those claims would invalidate the portion of the Scent-Lok patent making those same claims. The Patent Office document states, "The clothing of Popper is capable of being used to avoid detection of wildlife through the senses of smell as the clothing in its normal use is worn on the body." This seems to suggest that several of the claims in the Scent-Lok patent were already patented in the Popper patent.

The document further states, "The nonstatutory double patenting rejection is based on a judicially created doctrine grounded in public policy (a policy reflected in statute) so as to prevent the unjustified or improper timewise extension of the 'right to exclude' granted by a patent and to prevent possible harassment by multiple assignees."

In June, 2006, the Patent claims 1-10 of the originally applied for Scent Lok patent on activated carbon suits used for the purpose of eliminating human scent or odors hunting were rejected. However, Scent Lok resubmitted a claim for a new or revised patent, using different words and terms, but still using the same ideas, use and application.

As of September 13, 2007

Scent Lok no longer has a Patent on the use of activated carbon, or any other product, designed to reduce, control or eliminate odors while hunting.

May 1, 2007

What Odors does Activated Carbon Attract; The Truth about Reactivation

To find out how activated carbon works I recently spoke to a Ph D, who actually works for a company that manufactures activated carbon. He says that the little amount of carbon in most of the suits out there is not enough to eliminate 100% of the human perspiration odors given off by any hunter within the first 10 minutes of wearing the suit; because, if you look at the layer of carbon in the suits, it does not cover the entire area of the fabric. About 60% of the odors can escape from some of those suits, which means that you will be smelled by game animals if they are downwind of you.

This Ph D works for a company that manufactures activated carbon for use in clothing. He gains nothing by saying that many of the claims of scent control companies are false, misleading etc. In fact he may be losing future sales to those companies. The only thing he gains is self-respect - for telling the truth.

He says that if a hunter wants activated carbon suits to be effective on a regular basis, the hunter needs to buy disposable suits, because the majority of the suits on the market cannot be reactivated to the point where they will reduce even "most" of the odors a human produces for more than one or two times of using them for 4-6 hours on a hunt.

He also states that, because activated carbon does not "attract" (as in magnetic attraction or "suck in odors" due to some unnamed process), any odors inside the suit, that can exit the suit, without coming into physical contact with the activated carbon (which most of the odors can do, because of the numerous areas of the suits that are not completely covered by carbon), will go around the carbon, exit the suit, and alarm game animals. This has been proven in the undisputed facts of Shivik's dog study. And deer have about the same if not more olfactory receptors in their nose than dogs do, so they probably can smell at least as well as, if not better than, dogs.

The whole "regeneration" of the activated carbon in respect to human perspiration thing - is misunderstood. According to the Ph D, activated carbon is not selective in what it holds on to - meaning that every odor that physically comes in contact with the minute amount of carbon in one of these suits may be stuck to the surface of the carbon - as long as there is room for it.

And, therein lies the problem. Due to the minute amount of carbon in these suits, it is very likely that the minute surface area of the carbon can be filled up with odors, scents, vapors, molecules etc. from perspiration, smoke, gasoline, household odors, odors of leaves, dirt, decomposing animals, plants, etc, (as in any odor that is in the air anywhere you wear the suit), and it will probably fill up within the first few hours that you wear it.

So, after 1-2 hours, the suit no longer works to contain, stop or reduce human perspiration odors (no matter which of the several compounds that make up human odors you are talking about), because it is filled up with odors, from any source.

The Ph D tells me that he does not know of any activated carbon that can be reactivated (up to 90%) as some manufacturers claim, because some of the carbon itself is lost in reactivation, and some of the odors will not be "dislodged" from the carbon, because the molecules are just too long and complex to be dislodged at temperatures below 200 degrees.

He also states that dislodging of any odor, compound etc, on the surface of activated carbon is achieved when the "boiling point" of that odor or compound is reached in a "steam-environment", as in wet clothing being placed in a household dryer. Many odors (including some of the compounds in human perspiration) have boiling points above 200 degrees, which means a household dryer has to be hotter than 200 degrees to reactivated most of the compounds on the carbon. Most household dryers do not get hotter than 200 degrees, because it is not safe.

The Ph D states that the 90% regeneration rate claimed by some manufacturers is high, because it applies only to some of the compounds of human perspiration. And then there are all of the other odors the carbon comes in contact when you wear it. He states that regeneration is more likely in the range of 70%. An article on reactivation at Virginia Tech states it can be reactivated (at the right temperatures) up to 70%.

And, here is the big thing. The regeneration factor (let's say 80%) is the "original adsorbtion capability" of the carbon, meaning the ability to reactivate the carbon - the first time you put it in the dryer. So, only 80 percent of the carbon can be reactivated, and now you only have 80 percent left to capture odors. The next time you throw your suit in the dryer, you can only regenerate 80% of the 80% capacity left; which is 64 percent.

And the second time you use it - it fills up with odors faster than it did the first time, because it has less adsorbtion capacity.

The next time you put it in the dryer it will only reactivate to 51%, and now only 49% of your odors could (possibly) be trapped. The next time you put it in the dryer it is down to 40%, then 32%, then 25% and by about the 8th-10th time you put it in the dryer, it is useless.

But, if you don't put it in the dryer after every 4 -6 hours of use, it is useless anyhow, because it is full of all kinds of odors. And the deer will smell you if you use it before reactivating it.

So, you have to reactivate it. But, each time you reactivate it - it is less effective, and by the 10th time you reactivate or use it, it cannot work.

Those who believe they can work, because they can - for a while, should buy another activated carbon suit - every year.

If you who are wearing an activated carbon suit or clothing - that is over 4 months old, or has been through the dryer 8 times and you are still having good success with it - it is not because of the activated carbon in the suit - because the activated carbon has long since ceased to capture, eliminate, reduce or lock in any odors that you give off.

Your success is not due to the activated carbon in the clothing - it is because you are good hunters, you understand how the animals detect you by sight, sound and scent, and you take precautions to avoid being detected.

3/11/07

Is the Search & rescue Scent Lok Test Valid?

(Re: Do activated carbon suits fool the nose? - Article Below)

By T.R.Michels

Scent Lok has questioned whether the Shivik dog study (2006) was "scientific", or if it met "scientific standards". In response to that question Bruce Kimball with APHIS at the USDA National Wildlife Research Center states:

Subject: RE: Deer scent

From: Bruce.A.Kimball@aphis.usda.gov

Date: Wed, 21 Feb 2007 14:28:50 -0700

My "feelings" are not pertinent. The bottom line is that, like all research at the National Wildlife Research Center, Dr. Shivik's study was approved at every level before he initiated the study. Further, his research findings were published in a peer-reviewed scientific journal. Thus, his findings would absolutely be considered scientific.

A well-designed field study to assess the impact of carbon clothing on deer/hunter interactions would take a couple of years, several technicians, and at least $250,000 to conduct. If you are interested in funding such a study, I would be happy to discuss potential designs in detail.

Cheers

Bruce

I'll bet Scent Lok won't fund or participate in such a study.

3/10/07

Here is a response from noted white-tailed deer biologist and outdoor writer Dr. Karl Miller on the subject of the Shivik dog study:

Subject: Re: Deer and dogs smelling ability

In a way, it's difficult to compare a study on a dog's ability to locate scent, and a deer's ability- however, there likely are some important similarities. We know that dogs can be trained to do some amazing things with their noses - finding bombs and drugs, tracking fugitives, etc. If we could train a deer to do this, could they do equally well? I don't think there is any way to determine this.

I am not at all surprised that the dogs in the Shivik study were able to determine the human scent. I would have been surprised if the dogs were unable to detect it! Although I don't know how effective carbon clothing is at reducing potential odors, even if they were 99.99999% effective, the dogs probably could still find some scent.

Could deer do the same - perhaps. They may be a little more (or less) effective in identifying or detecting the scent, but unless scent is essentially eliminated there may still be enough there to detect. Personally, I do not think that there is any way that carbon suits can eliminate odors, but perhaps they can be effective at odor reduction (I do not have the experience to comment on this).

The military also uses activated carbon clothing, commonly referred to as Chemical Warfare Suits, but they are limited-use, disposable garments, not intended for multiple use, because, according to the paper The War Next Time: Countering Rogue States and Terrorists Armed with Chemical and Biological Weapons, the new JS-LIST suits worn by the armed services "provide 45 days of wear versus 22 days for the BDOs."

These chemical warfare suits have several times more activated carbon in them than the suits currently being offered for hunting purposes; and they only last for 45 days!

This document can be viewed on-line at http://www.au.af.mil/au/awc/awcgate/cpc-pubs/war_next_time/schneider2.pdf, or just type the words "JSList suits" in the search box on Google to read the above quote.

An interesting comment in the document states, "In addition they can be washed up to six times without losing protective qualities."

This suggests that clothing made with activated carbon becomes less effective every time it is washed. It also suggests that after six washings, the Chemical Warfare Suits, which are made to US Government specifications, and have more activated carbon in them than the activated carbon suits worn by hunters, are ineffective after six washings!

And yet - the loss of activated carbon due to washing, and the eventual ineffectiveness of the suits due to washing, is not clearly stated by the manufacturers of the activated carbon scent-elimination suits in any of their literature, or on their web sites. Note the reference to heavy perspiration in the following article, which will be talked about later.

In a further effort to determine whether or not a Scent Lok suit could significantly adsorb human odors, a piece of one of their suits was sent to Purification Process in Great Britain; which found that there wasn't enough activated carbon in the suit to even test.

3/1/07

Do activated carbon suits fool the nose?

By T..R. Michels

Scent Lok has claimed that their suits remove enough human perspiration odors from a person wearing their suits that deer cannot smell a person wearing their suits. They have also claimed that deer smell better than dogs.

Research shows that deer have up to 297 million olfactory receptors in the nose, plus a vomeronasal organ (that detects scents/odors) in the roof of their mouth. Dogs have up to 220 million olfactory receptors in the nose, plus a vomeronasal organ. Humans have up to 5 million olfactory receptors in the nose, but no vomeronasal organ.

If the number of olfactory receptors in the nose of an animal is any indication of its ability to detect scents, then deer have a better sense of smell than dogs, and could have detected the humans wearing activated carbon suits in the 206 Shivik study.

In a test with search dogs, by JA Shivik, Ph.D., forty-two people were hidden from Colorado search and rescue dogs. Twenty-one of the people wore activated carbon suits; twenty-one did not. The dogs found all twenty-one people who didn't wear activated carbon suits, and twenty of the people who wore activated carbon suits. There was no noticeable difference in the time it took the dogs to find the humans. It took the dogs 2.7 minutes to detect the humans who were not wearing activated carbon suits, and 3.4 minutes to find the humans who were wearing activated carbon suits.

Shivik's report states, "That the dogs detected humans wearing the suit indicates that the system failed to prevent detection of human odors." Since deer have a sense of smell equal to if not better than dogs, it is safe to assume that deer would have detected the humans too.

The report adds, "The suits are probably not worth the cost to researchers or managers who want to approach canids undetected."

They probably aren't worth $150 to $300 to hunters either, if they can't keep deer from detecting the hunters.

You can view this article at this address: http://www.aphis.usda.gov/wildlife_damage/nwrc/publications/02pubs/shiv024.pdf.

How Does Washing Affect Activated Carbon?

In 2005, the Scent Lok web site at http://www.scentlok.com stated:

"When and how to wash: During warm weather when only a T-shirt is being worn as an undergarment and heavy perspiration is occurring, it is advised to wash your suit periodically. During cool weather when heavier undergarments or layers are worn, there is no need to wash the suit. Washing does not have anything to do with reactivation, but does get rid of unwanted body oils (caused by perspiration), blood, and dirt. Washing a Scent-Lok suit can be done 1-4 times per season without fear of losing carbon from the suit. The permanent ClimaFlex treatment, that is on all Scent-Lok branded suits made during and after 2001, aids in the extraction of unwanted body oils in high perspiration areas when washed. Use only non-scented liquid clothes wash or preferably carbon wash. Once a garment is washed per label instructions it should be put in the dryer on a no heat setting until dry. Once the garment is dry, follow the reactivation instructions. ClimaFlex treatment is also a wicking agent, which adds to the overall comfort of the suit during warm weather."

Note: This article has since been removed from the web site. (Probably due to my comments on it.)

The comments in the US Government document mentioned above suggest that it is likely that the actions of both household washers and dryers may result in the loss of some of the activated carbon in the scent-elimination clothing worn by hunters.

Can Activated Carbon Suits be Re-activated as Manufacturers Claim?

Scent-Lok, one of the largest producers and the only licensor of activated carbon suits, states that their suits can be re-charged by placing them in the clothes dryer for 20 to 30 minutes to re-activate the carbon.

In 2005 the Scent Lok web site stated:

"How are odors released?
It is common knowledge that heat makes molecules move more rapidly. Reactivation is only obtained by using a clothes dryer. Reactivation is achieved by placing the suit in a dryer for twenty to thirty minutes on a medium to high heat setting or according to the label instructions. The heat from the clothes dryer creates what is scientifically known as Brownian molecular motion, which causes the scent molecules to move rapidly. This movement breaks the molecules free from the surfaces of the activated carbon particles and interior pores of the carbon, and allows them to eventually exit out of the dryer vent."

Note: This article has since been removed from the site. Pay attention to the words "Brownian molecular motion".

The use of the scientific term Brownian molecular motion on the Scent-Lok web site appears to add some credibility to their claims about activated carbon. There is no such term as "Brownian molecular motion". There is however a term known as Brownian motion, about which this web site states, "Brownian motion (or Brownian movement) can be defined as the random movement of microscopic particles suspended in a fluid."

Brownian motion has nothing to do with the re-activation or desorbtion of activated carbon, because the term is only used in reference to "particles suspended in a fluid"- not to the motion or activity of gaseous odor molecules released by activated carbon that is subjected to heat in a clothes dryer.

Activated Carbon Re-Activation Facts

In defense of the statements that their suits can be re-activated Scent Lok maintains that the word "reactivation" is a loosely used term. In reality "reactivation", as it applies to activated carbon, means that the adsorption capability of the carbon has been totally and completely re-activated. Scent Lok has stated that the garments aren't "totally reactivated" after they are first washed and put in the dryer, but that they are partially "regenerated" or "desorbed". Supposedly this partial regeneration is enough to allow the clothing to again adsorb more odors. While some desorption or "regeneration" can occur when activated carbon is exposed to temperatures lower than 750 to 1200 degrees F, there is a point when the temperature is too low to "reactivate" activated carbon.

In order to completely re-activate activated carbon, processes referred to as "Drying", "Desorbtion", "Pyrolysis" and "Gasification" are used. To completely re-activate an activated carbon suit saturated with human perspiration it has to be heated to about 800 C or 1472 F. And it would have to be done in a controlled atmosphere with low oxygen concentration to reduce the possibility of combustion. This is clearly stated in the U.S. Army Corps of Engineers - Engineering and Design, Adsorption Design Guide, Design Guide No. DG1110-1-2, which can be viewed on the internet.

At 500 degrees F the suit will be nothing but carbon. Even if desorbtion was possible most household clothes dryers do not reach temperatures over 200 F, which is not high enough to release the trapped odors in the scent-elimination suits. It is highly unlikely that activated carbon suits for hunting use can be recharged, with the result that the suits will eventually become full of odors, to the point where the charcoal will no longer trap odors.

Following is an article on the "reactivation" of activated carbon from the Civil Engineering Department of Virginia Technical University at http://www.ce.vt.edu/program_areas/environmental/teach/wtprimer/carbon/sketcarb.html. It was not written to refute the claims of the activated carbon hunting suit industry, but rather to explain how activated carbon works, and how it can, or in the case of the powdered carbon used to manufacture cannot be reactivated at temperatures under 212 degrees Fahrenheit.

The "spent" carbon, as it is called, is removed and sent for re-activation treatment. This is done primarily with granular activated carbon because PAC (powdered activated carbon) particles are too small to be effectively re-activated. This process allows for recovery of approximately 70% of the original carbon. This number also allows for any physically lost in the shipment process. The re-activated carbon is then mixed with a portion of new carbon for higher effectiveness and is then returned to its place in the plant process (Clark, 1989).

Reactivation Process Specifics

Desorption, 100-649 degrees C, volatile materials driven off

Gasification, 649-1038 degrees C, vapors and residues from previous stages driven out of pores

One hundred degrees Celsius is equal to 212 degrees Fahrenheit. This is the extreme low temperature during which "partial desorption" of odors and gases may occur. However, as stated above, most household clothes dryers produce less than 150 degrees Fahrenheit; which suggests that the activated carbon suits sold to hunters cannot even be "partially regenerated or desorbed".

The following quote is from the NORIT Activated Carbon web site at http://www.norit-ac.com/newsevents.asp?newsId=106. Note that it is about activated carbon used for air; not only water.

NORIT's reactivation service is a cost-effective and environmentally sound solution. 'The recent implementation of the EU Landfill Directive in the UK is further boosting interest in thermal reactivation of exhausted GAC,' comments Mark Currier, NORIT UK Sales Manager. During thermal reactivation, the exhausted granular activated carbon (GAC) is heat treated in dedicated kilns at temperatures exceeding 900 C. Adsorbed organic compounds are cracked and oxidized. Following reactivation, the GAC's adsorptive properties are restored to a level comparable to that of virgin GAC. As a result, the GAC can be reused in the same or a similar application.

Exhausted carbon: green and amber;

The relevant EU regulation categorizes exhausted GAC as either green (used in water purification and food production) or amber (used in the treatment of gas/air or wastewater). NORIT reactivates green and amber GAC in completely separate systems, precluding the risk of cross contamination.

The above quote shows that activated carbon for air is reactivated (de-sorbed) at temperatures above 900 degrees C. Again, no hunter has access to such a dryer, and if he did, it would incinerate his suit.

The following quote is from the CPL Carbon Link web site at http://www.activated-carbon.com/5-1.html.

Reactivation restores the activated carbon to a state where it is virtually identical to the properties of the virgin pre-cursor. This is done by undergoing the process of activation a second time rather than simply displacing adsorbed organic material by processing at high temperature. The organic compounds removed from the spent adsorbent are passed through a sophisticated multi-stage treatment system ensuring the reactivation system does not cause pollution while undertaking a recycling operation.

The above quote states that "reactivation" to the state of the virgin precursor occurs after high temperature has been used to "desorb" the carbon, and then it has to be reactivated "a second time".

It appears that "reactivation" (which is the term used by Scent Lok) is even more difficult than desorbtion. And it is unlikely any hunter has access to a facility to reactivate their suit; or the money to do it.

The following quote is from the Inist web site at http://cat.inist.fr/?aModele=afficheN&cpsidt=16558801

Bench-scale experiments investigated the effect of electrolyte mixing on the effectiveness of an electrochemical reactor for the reactivation of granular activated carbon (GAC). Two different GACs (F-400 and WV-B) were loaded with phenol via batch adsorption tests, then electrochemically reactivated and finally reloaded with phenol. Reactivation was conducted in a recirculating flow reactor with a 0.1 M NaCl solution as the electrolyte. Cathodic reactivation was more efficient than the anodic reactivation and increasing the degree of electrolyte mixing decreased the cathodic reactivation efficiencies, while there was no significant change in the anodic reactivation efficiencies. Higher degrees of electrolyte mixing decreased the local pH at the cathode and consequently reduced the desorption driving force and therefore reduced the reactivation efficiency. The electrolyte mixing lowered the cell voltage. However, this advantage was overshadowed by the increased energy consumption required for the electrolyte pumping, the reduction of the oxidation rate of phenol, and a 20% reduction in the reactivation efficiencies. Thus, electrolyte mixing of the electrolyte is not recommended in the electrochemical reactivation of GAC.

Note that this method includes "electrochemical reactivation", which no hunter I know of has access to.

The following quote is from the Cameron Carbon web site at http://www.cameroncarbon.com/spent_carbon.html

Cameron Carbon offers spent activated carbon reactivation (recycling) services at a fully permitted reactivation facility. Spent carbon is recycled in specially designed high temperature furnaces that can restore the carbon's pore structure to new or near new quality. The organics that are vaporized from the spent carbon are fully destroyed downstream of the furnace by an air pollution control system. Certification of VOC (volatile organic compounds) destruction can be provided upon request.

The above quote states that "reactivation" (the word Scent Lok uses) occurs when activated carbon is placed in "specially designed high temperature furnaces", and ONLY THEN is it restored to new or nearly new quality. No hunter I know of has access to such a facility.

The following quote is from the CMCC-AC web site at http://www.cmcc-ac.co.jp/english/product/catalog1.html

Activated carbon that has dropped its adsorbing capability can be recovered in its performance by the reactivation process and can be used in the adsorption process again. When activated carbon adsorbs impurities, a balanced relationship of adsorption is established among the adsorbate (i.e. substance adsorbed by activated carbon), activated carbon, and medium (i.e. substance surrounding the adsorbate and activated carbon such as water or gas).

Reactivating means that this balanced relationship of adsorption is changed and adsorbate is separated from activated carbon. Depending on the reaction mechanism, there are 6 types of reactivation; decompression reactivation, heating and leaving reactivation, chemical reactivation, solvent reactivation, substitutive reactivation, and oxidation and decomposition reactivation.

I don't know of any hunter who has access to 5 of the reactivation types, and we have already established that even partial reactivation, or "desorbption" (odors as it is called) of human perspiration, must occur at temperatures over 212 degrees F.

The following quote is from the Siemens web site HERE

Our carbon reactivation facilities processes RCRA hazardous and non-hazardous liquid and vapor phase spent carbons. After inspection and acceptance, the spent carbon is heated to 1600°F to ensure proper reactivation. The cooled reactivated carbon is identified by lot numbers. Each carbon lot is sampled and analyzed in accordance with Westates' QA/QC program. This process assures you receive the highest quality reactivated carbon. The entire process is computer controlled and monitored, ensuring the facility meets or exceeds federal and state regulatory requirements for air and water discharges. A "Certificate of Reactivation" can be issued for each shipment of recycled carbon. This certifies that the spent carbon has been recycled in a manner that meets or exceeds all applicable RCRA and Benzene NESHAP regulations.

I don't know of any hunter who has a 1600 degree dryer.

I personally spoke to a Chemist at 3M here in St. Paul, MN. He told me that due to the length of the human perspiration odor it would be impossible to desorb it from activated carbon at temperatures below 500 degrees F. At this temperature the suit would be incinerated.

8/12/07

How Activated Carbon Can (not) Work

A chemist who works in the activated carbon industry, specifically in the manufacture of activated carbon for use in clothing, stated in an e-mail on June 28, 2007:

"As regards reactivation - it is true that carbon can only be reactivated industrially by high temperatures and/or low pressures. Activated carbon can be partially regenerated by driving off the adsorbed species with heat. However, one tends to require temperatures, which are close to or exceed the boiling point of the adsorbed species. For example to regenerate some activity for carbon tetrachloride - temperatures of the order of 100 to 120 F or higher would be required for a significant removal. For removing butyric acid - a compound produced by bacterial action on sweat - temperatures nearer to 200 F would be needed, certainly beyond most dryers (and most clothes!)."

In other words, the odor or scent of bacterial action on human perspiration (butyric acid), which Scent Lok claims can be desorbed from activated carbon by "re-activating" it, cannot be removed from activated carbon clothing by using a household dryer (which normally does not reach temperatures higher that 165 degrees F).

More Information

After watching the FOX Television investigative report on Scent Lok - one chemist who worked with activated carbon responded with this:

"One thing that I caught on the DVD was the scene with the sponge. If I heard correctly, she stated that carbon like a sponge could hold many times its weight. At best carbon can only hold about half its weight."

I think that clears up a lot. If the amount of activated carbon in a Scent Lok suit is less than 4-5 ounces, it means that the suit can only hold 2-2.5 ounces of perspiration and perspiration odor. I'm sure most of us sweat 2.5 ounces in a few hours, and we have to add in all of the other odors collected. So, the suit probably lasts only a few hours. But most hunters wear it all day; which means they have to recharge it every day.

New Underhanded Tactics by Scent Lok

I was informed on May 2, 2007, that in their recent Patent re-exam, Scent Lok accuses me of trying to get them to bribe me to not post, talk about or write about my proof that their product cannot work as they claim. The truth of the matter is that I did try to get them to bribe me, in either an e-mail or a signed letter, so that I would have proof of their willingness to bribe me, so I could expose their tactics to the public. I never intended to accept a bribe from them.

I came up with the idea of trying to get them to bribe me after Mike Andrews (of Scent Lok) made the following statement to me: "We look forward to having you as one of our biggest supporters in the future." I took that as an offer to compensate me if I would no longer comment on my beliefs about how their product could not work as they claim.

Here is what I e-mailed Scent Lok on May 2, 2007

Scent Lok:

I understand that your company has accused me of trying to get you to bribe me in your latest patent re-exam. The truth of the matter is, is that I wanted to see if you would offer to bribe me (in an e-mail), so I could expose it to the public. What I wanted to do was show people how far your company would go to shut me up.

Obviously someone at Scent Lok correctly figured out that my belief in the fact that your product does not work (and my Christian morals) would not allow me to accept a bribe from you to keep me quiet about the fact that I do not believe your product works; and therefore Scent Lok did not attempt to bribe me.

So, my ruse failed. And you know what - I will pay for a voice stress test on myself to show that I am telling the truth in this matter. Can you say the same?

If you do not have any reference to me removed from that patent re-exam immediately I will be forced to seek legal recourse.

I have kept a record of this, and will be forwarding a copy to the Patent and Trademark Office.

I know for a fact that you are required by law to bring my explanation of this matter to the attention of the Patent and Trademark Office. If I do not receive a notification from the Patent and Trademark Office, of your notification to them of my explanation of your twisting my intent in this matter, I will contact them myself. I just got off the phone with Mr. Andy Kashnicow (sp?), and he told me who to contact and what to do.

This is all going on my web site, and it is being e-mailed to every editor I have in my database, so they will all know about your tactics.

In your current re-exam you failed to tell the Patent Office that the following quote is on my web site. It clearly states that I would not accept a bribe; you must notify the Patent Office of this too.

T.R. Michels

In the earlier response to me Mike Andrews stated:

"We look forward to having you as one of our biggest supporters in the future."

My response:

Scent Lok - you don't have enough money to buy me off, or to keep me from writing the truth about your product. My integrity and reputation as a Christian, and as an outdoor writer, author and seminar speaker - is on the line.

In another e-mail I wrote:

Scent Lok:

If I do not receive an e-mail from you by May 10th, I will contact the Patent and Trademark Office about this matter. And I will have at least one US Legislator behind me when I do it.

I also intend to contact Trish Van Pilsum at FOX news about this, she is a friend of mine.

May Yahweh bless you according to your deeds,

T.R. Michels

Can Activated Carbon Suits Work, As Manufacturers Claim?

Is there enough activated carbon in a Scent Lok Suit to Work?

The Columbus Industries Patent Application # 5,678,247 states:

The layer of odor absorbing material (activated carbon) should be at least 1/8 inches thick to provide sufficient activated carbon and very importantly provide a higher residence time of the human scent within the odor absorbing layer to achieve greater odor adsorbing efficiency. It is more preferred to employ a thickness of about 1/4 inches for the odor absorbing sheet layer.

I personally separated the layers of a Scent Lok in August of 2006, to determine how much activated carbon was in the suit. I first noticed that there was not enough activated carbon to cover the entire surface of the fabric, which meant that odors could go through the suit without ever coming into contact with the activated carbon; making the suit ineffective.

The layer of activated carbon in the Scent Lok was less than 1/8 inch, probably more like 1/50 of an inch. But, in its patent, the above company states that there needs to be at least 1/8 inch of activated carbon, and "it is more preferred to employ a thickness of about 1/4 inches" of activated carbon to provide sufficient "odor adsorbing efficiency".

This Patent, which may be for the material Scent Lok uses in its clothing, states, in this US Government document, that there is not enough activated carbon in Scent Lok suits, to work!

Want to reduce odors while you hunt? Here is what you can do.

Hint: Don't rely on Activated Carbon Clothing

It is bacteria on the skin that produces the odor associated with human perspiration. What scent elimination products and clothing are trying to do is eliminate at least that smell. Obviously the best way to do that is to eliminate the bacteria; and bacteria needs moisture to grow. So - to reduce human perspiration body odor:

Use antibacterial soaps and shampoo, (that don't smell) every time - before you hunt.

Use an anti-bacterial clothes spray (Scent Killer spray by Wildlife Research) to thoroughly saturate your clothes, then let them dry.

Use an antibacterial gel or lotion that will kill re-growth bacteria (it will only take an hour or more for bacteria to grow and start to smell), clothing, and/or on you body (in areas where it is most likely to grow [which are areas that contain moisture]) such as your armpits, butt, groin and head, and beard (if you have one). This includes Scent Killer (by Wildlife Research), Sport Wash and N O Dor (by Atsko/Sno-Seal), Scent Shield (by Robinson Labratories)

Use an unscented antibacterial deodorant (to reduce any odors you do produce later on - after bacterial re-growth).

Wear moisture wicking underwear, such as polypropylene, Under Amror etc. To keep body moisture to a minimum (so bacterial growth is slowed down).

Wear clothing with antibacterials, such as triclosan, mycosan or silver, to kill re-growth bacteria (while you hunt). Clothing designed to kill bacteria, using mycosan, triclosan or silver, needs to be worn against the skin. This includes Contain, X-Scent and Eliminator under garments.

You can make your clothes smell like the local surroundings by putting your clothes in a container and throwing in leaves, needles or dirt form the area.

Do not wear your hunting clothes, boots, gloves or hat until you get out of your vehicle, or the gas station or restaurant before you hunt, you may pick up scents that will spook the deer.

Clothing such as No-Trace and Eliminator (which both use cyclodextrin), can reduce odors all day long, and all you have to do is rinse it (no soap) in cool water to reactivate it. You can wear these clothes against your skin or not, but, if you wear a shirt, pants and hat of it - there is no need to buy an expensive jacket of it (unless the only jacket you have already smells).

Page 3 - Misleading Terms & False Statements used by Scent-Lok