It’s about as close to an invisibility cloak as a hunter can get.

When it comes to successfully bowhunting big game, not allowing an animal to get a snootful of you can be far more important than camouflaging your profile—and who among us has not been subjected to the soul-crushing scene of a big boy buck, bull, or bear throwing his nose to the wind and huffing off out of range?

Fortunately, several top companies in the outdoor industry have been working for decades to help hunters get closer to their game by suppressing the human scent that spooks prey. All number of chemical stews have been brewed into shirts, jackets, and pants—some of it snake oil, some of it backed by testing and science.

So how is a hunter who’s fixing to plop down some serious coin for a new set of duds to choose? To help narrow the choices down, we spoke with three of the top companies in scent- control outerwear to see how they build a barrier between a hunter and the odors he emits. Each takes a different approach to the problem, but all are based on solid science and technical knowhow to help you get closer to your game.

Kill It Or Capture It?

Essentially, there are two ways to attack scent emanating from the human body that hunting clothing makers have settled on; either kill the smell before it stinks, or capture it once it has been created.

According to experts, when the human body creates sweat, it emits moisture and certain chemicals through the pores. Alone, that combination doesn’t begin to smell until it interacts with bacteria on the body. Once that bacterium interacts with the body’s perspiration, it breeds and creates that body odor we all know and try to avoid. That’s what deer, elk, and other game can smell and pick up on well before they can see you.

It’s here where we begin to see the different strategies for scent control. Some technologies attack the growth of the bacteria that interacts with the body’s emissions in order to cut the smell before it actually stinks. Other technologies simply try to suck up the smell after it’s created, keeping a barrier between the hunted’s nose and the hunter’s body.

That may all sound a bit like voodoo science to the everyday hunter, but this kind of odor mitigation can be verified in a lab. While most gear makers are careful to say their technology doesn’t eliminate all scent, they do wrestle over who does the best job. And, according to scientists in this field, the only way to eliminate all scent from the human body is to encase it in the equivalent of a space suit, but that’s not exactly how most hunters want to spend their time in a treestand or on the mountain.

The Carbon Solution

One of the top names in scent control technology for sportsmen is Scent-Lok Technologies. The company’s been in the business of helping hunters get closer to their game since 1992, and engineers with the company have been testing a variety of technologies to get the stink out for decades.

According to Scent-Lok, there’s no better way to keep a hunter’s smell at bay than by taking the adsorption approach. Yes, that’s adsorption with a “d.” Whereas a sponge absorbs water by dissolving the liquid into the solid sponge, adsorption happens on the molecular level, almost like a magnet attracting the scent molecules to a particular substance.

Scent-Lok combines three things—activated carbon, another specially treated carbon that they say adsorbs the hydrogen sulfide typically found in human breath, and a mineral called zeolite, which is effective in adsorbing other kinds of powerful odors, like ammonia. According to Scent-Lok, the combination of the three materials gets as close to that invisibility cloak as a hunter can get.

“Testing has shown that activated carbon can adsorb up to 99 percent of human-specific odors,” Scent-Lok says. “We want that other 1 percent.”

Scent-Lok swears by the well-known method of using activated carbon to suck in all the scent created by the human body. And they say they have the science to prove it works and that it works better than anything else on the market today.

In December, the company provided a list of both its own and its competitors’ garments to a well-known testing lab at Rutgers University in New Jersey, who then went out and purchased those garments so it would be able to conduct side-by-side comparisons. According to the test report, the Scent-Lok materials using its “Carbon Alloy” technology kept nearly 100 percent of the odor from coming through the garment for an astonishing 24 hours.

“In my experience, activated carbon-based products tend to outperform all the other types of fabrics in these tests,” said Dr. Tom Hartman, director of the Center for Advanced Food Technology’s mass spectrometry lab at Rutgers University, who conducted the study.

Hartman, who for nearly 30 years has been doing laboratory testing to validate the effectiveness of scent control products for a variety of industry clients, was paid by Scent-Lok to conduct the study and has served as an expert witness in recent lawsuits against the company. But he said he’s not an employee of Scent-Lok and has done similar tests for competitors in the hunting market.

“I’m independent. I don’t advocate products. I could care less about [Scent-Lok’s] product,” Hartman said. “I do the tests and if it’s good for them, that’s fine, and if it’s bad for them, hey, what can I tell you?”

In fact, Hartman was skeptical enough of the initial Scent-Lok test results that he increased the amount of odor and still got 99.8 percent of the odor blocked by the Scent-Lok material.

“Seeing nothing, I increased it 10 times, and I could start to see a couple of tiny peaks breaking through the [Scent-Lok] fabric,” Hartman said.

But Hartman did say that carbon alloy products like Scent-Lok do so well, he’s had other companies refuse to pay him when he delivers the results.

“I’ve done this time and time again,” Hartman said. “I’ve even had customers in the past where I took their products and tested them against carbon-based products, and the results were so dramatic that the carbon products outperformed their products so much they actually got mad at the results and didn’t want to pay their bill for the study.”

A Combined Assault

So what about the other approach to scent mitigation—attacking the smell before it stinks?

Few hunting gear makers rely simply on what is called “anti-microbial” technology alone. One company—Under Armour—takes a combined approach in its line of Scent Control garments,  using threads reinforced with silver to attack the odor-causing bacteria and a man-made version of zeolite to adsorb any odors that are formed. Silver is used by a variety of clothing manufacturers to inhibit body odors, including some in the hiking and military markets.

Under Armour was founded in 1996 by Kevin Plank, a 23-year-old former University of Maryland special teams captain who, back in his playing days, hated having to change his sweat-soaked cotton T-shirts over and over again during two-a-days. Plank named his new company Under Armour, and after extensive research on the athletic benefits of synthetic fabrics, designed the first Under Armour HeatGear T-shirt, which he named the #0037. The rest, as they say, is history.

But silver? The use of silver in medicine is nearly as old as medicine itself. Hippocrates is known to have used it to treat ulcers and wounds, the Romans almost certainly knew of its healing properties, and its use continued through the Middle Ages and up to the present day. Technically speaking, silver ions, which flow from nanoparticles when oxidized, are deadly to bacteria. Silver nanoparticles are used just about everywhere, including in cosmetics, socks, food containers, detergents, sprays, and a wide range of other products to stop the spread of germs.

“The Under Armour approach is a combination of a synthetic zeolite that’s infused with silver,” says Under Armour spokesman Eddie Stevenson. “The zeolite captures the human scent molecule and the silver helps keep the bacteria from growing and creating the smells.

“Nothing is 100 percent. Anyone who says that is wrong,” he added. “But it’s the best defense we have for adding into clothing.”

Stevenson says the advantage of the silver ion/zeolite combination means the garments can hold up to more abuse and keep their odor mitigation properties for longer.

“One of the main points from Under Armour Scent Control technology is that it does recharge in the wash,” says Stevenson. “It doesn’t take heat, it doesn’t take drying like carbon. It totally cleans itself and recharges in the wash.”

Stevenson said Under Armour’s Scent Control technology has been independently tested, but the company declined to provide their test results for review.

The Polymer Play

On the other end of the spectrum is the Trinity technology from Robinson Outdoors. Bill Robinson founded the company back in 1985 with Scent Shield, a scent-eliminating spray product. In 1997, ScentBlocker clothing was born using activated carbon fabrics. The ScentBlocker name is well known in the hunting community as a leader in the odor-mitigating garment world, and hunters have sworn by these garments for years.

The company offers a range of scent control technologies, including S3 silver anti-microbial garments. Basically, ScentBlocker S3 hunting wear is made with threads that are impregnated with silver ions, which attack bacteria as they try to interact with human sweat. The silver ions “bind and penetrate the surface of odor-causing bacteria on contact,” the company says, killing them so they can’t produce the scent game can smell.

But ScentBlocker admits S3 can’t stop odors that already exist from spooking game, so they’ve invented a whole new way to stop the stink before it reaches the nose of a wily buck. Dubbed “Trinity,” the ScentBlocker technology is essentially a synthetic version of carbon that the company says is more adsorptive than any other substance out there.

“This is a wholly synthetic material and is designed to be optimized to work on human odor,” says ScentBlocker Marketing Director Mike Swan. “It took ScentBlocker nine years to develop Trinity.”

The Trinity polymer is applied to the surface of a garment in a “dot matrix” pattern and consists of so-called “macropores” and “micropores” that trap the odor molecules and move them deeper into the matrix of the material without letting them escape to the outside. Think of it as a kind of Gore-Tex for BO.

“The secret to Trinity’s new technology is the use of a very fine particle size of synthetic polymer, which produces a micropore structure that creates an extraordinarily large surface area,” the company says. “This yields a weight-to-adsorption ratio that sets a performance standard previously thought to be scientifically impossible.”

ScentBlocker says simply throwing the garment in a dryer at high heat can recharge the adsorption capabilities of Trinity. This breaks the physical attraction between the odor molecule and the Trinity material, making it ready for another sweaty day in the field.

“We’re getting away from this brouhaha between scent control gear makers,” Swan said. “Let everyone else worry about tests.

“What we’re focused on is not only  making our scent control better because that’s what we do, but our garments are better,” he added. “We have better features, they’re better cut, better materials, better zippers—we’ve got it all in there.”

A Question Of Confidence

Now that your brain is buzzing from all this talk of adsorption, macropores, and zeolites, where should you put your hard-earned cash to make your next hunt more successful?

As the testing shows, it’s clear that anti-microbials alone can’t do the trick. Experts say keeping a layer of silver-impregnated clothing close to the skin to help kill as many of the odor-making bugs right at the stink factory is a good start. But you’re still going to smell bad at some point, so a little adsorption is still in order.

It’s hard to say which way to go. Experienced hunters know that beating an animal’s nose, even for a few moments, can make the difference between success and failure. They also know that doing so requires more than just throwing on a set of expensive scent-control outerwear, that they must follow a meticulous scent-control strategy that includes using scent-free laundry products, showering regularly using shampoos and soaps designed for the purpose, and keeping all their hunting gear, including packs, footwear, and more, away from ancillary odors that can alert game that something is amiss.

Each of the major clothing manufacturers we talked to has a strong following of serious hunters. In terms of laboratory testing, Scent-Lok was the only one of the three to provide us access to their testing data. Each of the three uses a different method to try to combat human stinkum.

And all are a darn sight more comfortable than an astronaut suit.