If you hate mosquitoes as much as we do, you've probably tried a few different solutions to get the blood-sucking pests to leave you alone.

One of our favorite solutions for wide-area mosquito repellent comes from Thermacell. Most of the company's repellents work by heating a chemical compound called allethrin, which is a synthetic version of a naturally-occurring compound found in the chrysanthemum (mums) flower. Heating the compound creates a not-unpleasant smelling smoke, which for some reason mosquitoes hate. As the smoke swirls around you, a mosquito-free barrier zone is created — at least in theory.

Photo: DVIDS / Petty Officer 3rd Class William Phillips

Photo: DVIDS / Petty Officer 3rd Class William Phillips

The Insect-Infested Proving Ground

The Thermacell system was first introduced to us by backwoods Florida hog hunters who spent countless motionless hours in the swampy fringes of the Everglades. Since then we’ve fielded it successfully in places where slapping DEET on your skin just doesn’t cut it. We’ve used it during wilderness search-and-rescue scenarios in the thick woods of north Florida’s Camp Blanding, but for an unparalleled mosquito-filled proving ground, we had to head further south.

We ventured to the truly nightmarish mangrove swamps of Collier-Seminole State Park as well as Big Cypress National Preserve in Florida. Seminole-Collier is acknowledged by park rangers to contain some of the highest mosquito concentration in South Florida, which basically means it's one of the most mosquito-dense regions in the nation. The meter at the park entrance, where we’re used to seeing a “Fire Danger” sign, instead lists the level of mosquito activity ranging from low, to high, to “Blood Donor.”

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Tree Snail Hammock Trail was one of the most mosquito-dense areas we encountered.

Naturally, during our time there, the meter was pegged to the far side for the entire duration. If our repellents could survive this gauntlet, they'd be worth every penny.

New Thermacell Mosquito Repellent Products

We used two of Thermacell’s newest products during this testing and evaluation trip: the Thermacell MR450 and the Thermacell Backpacker.

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The MR450 (pictured above) is basically an upgraded version of the classic MR150 portable repeller, which is what we’re used to carrying. The repeller contains a small butane cartridge to heat a metal griddle, which in turn vaporizes the allethrin repellent mats.

The mats start out blue when they’re impregnated with allethrin, then turn to white as the repellent wears out. When the whole mat turns white you simply swap it out with a new blue mat. The unit is available at an MSRP of $35, and a 120-hour refill pack of mats and cartridges is $45.

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The improvements for the MR450 model are incremental, but we do like it better than previous models. These changes include a rubberized grip for improved ergonomics and noise dampening. Also, the ignition switch was redesigned to make less noise when you light the flame.

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The Backpacker version ($40 MSRP, pictured above), on the other hand, represents a drastic departure from the prior designs and is more compact and minimalist. The primary difference is that it can use regular butane canisters (like those from MSR, Jetboil, etc.) instead of the proprietary Thermacell butane cartridges. There are a few good reasons for this.

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First, it means that you can buy your fuel at any campground store or Wal-Mart on the way to your destination, and have a bigger supply of fuel to scavenge from in emergencies. Also, you’ll save on your overall carried weight, since butane canisters may already be the primary fuel for your camp stove. Note, however, that the Backpacker does not work with the green Coleman propane canisters because they have a unique thread pattern.

Testing on the Trail

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Thermacell claims that these units extend protection up to 25 feet away, and that the greatest protection is offered up to 7.5 feet away, thus providing a 15’x15’ “exclusion zone.” The manufacturer further claims that within that shorter distance, the device provides between 95% to 98% effectiveness.


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These are some pretty big claims, and we wish that we could agree completely with them. Unfortunately, our field testing experiences don’t quite match up to these bold statements.

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First, let’s look at the effective radius. Based on our experience with the older versions as well as these newer products with identical claimed performance, we never once observed the repellents working that far out. At most the zone of maximum effectiveness is about a 4’x4’ area.

In our experience each person needs to have their own personal repellent device. You can’t depend on the device of the person sitting or walking next to you. It’s absolutely true that the observed performance of the Thermacell is to create your own personal anti-mosquito “bubble.” But it’s just that — a personal bubble, not a group bubble.

This may be due in part to wind conditions. The scent from your Thermacell may be blowing away from you, so having more than one unit is definitely preferable. For example, if walking in a straight line down a trail with the wind at your face, the scent will be blowing behind you. But if your partner is ahead of you with theirs turned on, you’ll be covered both front and back. And obviously the reverse applies when the wind shifts.

For the record, Thermacell says that its products are intended for stationary use, so we would probably see even more effective coverage if remaining stationary.

Next we come to the 95% to 98% effectiveness claim. In our experience, the Thermacell will never provide a complete barrier against mosquitoes — and that's understandable. Even the manufacturer doesn’t claim that.

By our own non-laboratory field estimates, we would guess that the system reduces mosquitoes landing on you by probably 80% in heavily-concentrated areas with aggressive mosquitoes. In lightly-concentrated areas with less aggressive mosquitoes that number probably comes closer to 90%.

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We came to this conclusion by walking the same section of trails multiple times — once with the Thermacell activated and once without. On one particularly fierce stretch of swamp called the Tree Snail Hammock Trail in Big Cypress National Preserve, we actually had a few mosquitoes land directly on the unit we were carrying in our hands.

We’re not dogging the product, we’re just saying that sometimes the effectiveness of a repellent depends on how hungry err… thirsty a mosquito happens to be.

As long as you know what you’re getting into, this is not a problem. We’ve used Thermacell mosquito repellents for years and will continue to use them, especially now that we have our hands on better versions of already-effective products. It’s not a magic bullet, but it is a highly-effective and relatively-inexpensive $25 to $35 tool which greatly increases your comfort and decreases the likelihood of contracting insect-borne diseases.

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If you really want 100% effectiveness you’ll likely have to combine a Thermacell device with a mosquito jacket and head covering, long sleeve shirt and pants, and also a DEET-based liquid repellent on your skin. That’s the combination of products that we used during our evaluations. It allowed us to slowly walk through and linger in sections of wilderness which unprotected humans would never be able to handle.

For more information on insect repellent strategies, check out our feature article “Bugging Outbreak” in RECOIL OFFGRID Issue 21, on sale now.

Here on OFFGRIDweb, you can also read our article on how to make smudge pot mosquito repellent, review a useful mosquito season infographic, or look at some of Thermacell's mosquito repelling lanterns.

About the Author

Andrew Schrader is a licensed professional engineer and is certified by the U.S. Army Corps of Engineers as an Urban Search and Rescue (USAR) Structures Specialist. His company, Recon Response Engineering LLC, advises state and federal government organizations on the subject of urban search and rescue and building collapse. He recently assisted the U.S. Department of State’s Italian Consulate in the development of their post-earthquake response and rescue protocol. You can follow him on Instagram at @reconresponse.


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