Introduction: Improving Your Thermacell

If you like to spend time outdoors, whether camping, fishing, hunting, etc., you probably already have one or more of the Thermacell insect repellant devices. These devices have a reputation as the best on the market for their purpose. Since they are so popular, I thought I’d pass along several of the things I have done with mine to reduce costs, and things I have done to make mine more “user friendly.”

The "Cost-to-operate" is something most everyone notices first. Making the OEM butane bottles refillable will save considerable money on butane and extend the life of your Thermacell devices. Refilling with a better quality of butane (quad-filtered, 9x filtered, etc.) only costs about $2 more per can than the standard quality used by the OEM and there are literally none of the fuel feed problems experienced with the OEM butane. With better quality butane the units usually start with a single button press rather than multiple button presses required for the OEM butane. Locally, my OEM butane cartridges/bottles cost $3 each. Refilling with quad-filtered butane costs about 31 cents per bottle and filling with 9x-filtered butane costs about 46 cents per bottle.

Re-coating your used OEM mats (rather than throwing them away) will save a considerable amount of money over time as well. I have also noticed that my re-coated mats last longer than the original OEM mats, saving even more money. Locally, OEM mats cost $1.16 each and normally last about 5 hours (advertised as 4 hours max). Re-coating the used OEM mats costs between 22-33 cents each depending on the number of pads re-coated and how much solution is applied and last over 6 hours. The length of time the mat repellant is effective depends on the environment (how thick the insects, etc.), so your times will probably vary from mine.

In this Instructable I’ll cover the following:

Step 1 – Refillable Cartridges (butane bottles)

Step 2 – Re-coating the Repellant Mats

Step 3 – DIY Thermacell Stand

Step 4 – Installing a Fuel Level Label

Step 5 – How to Make Viewing of Fuel Levels Easier

Step 6 – Make a Mat Holder Insert for the Thermacell Holster Pocket

Any tools and materials are identified in each step.

Step 1: Refillable Cartridges (butane Bottles)

Tools & materials needed

- Original Empty OEM Butane Cartridges

- Sharpie

- PenTool Shop 242-999 Pencil Torch (Harbor Freight Torch 94185 - has a Ronson style valve)

- Drill & 13/64” drill bit (use a 11/64” drill bit for Ronson valves)

- ¼” slotted screwdriver (for Ronson valves use a CR-V 10 specialty bit or a Ronson installation tool)

- Magnet

- Epoxy glue

There are two ways of refilling Thermacell butane cartridges: 1) remove the check valve of the cartridge and then use a modified butane can tip (sanded-down, cut tip, etc.) to fill from the top, or 2) install an in-let butane refill valve.

After getting new butane cartridges, the first thing I do is to mark the current levels of fuel in each. If you plan to use method one above (removing the check valve), then you only need to mark the level of fuel at the top of each bottle (figure 2). If you plane to install an in-let valve, then you mark the level of the fuel on both ends of each bottle (figure 3). The marks serve two purposes: 1) the full mark level when filling, and 2) and to check for a leak (it could be days before you remember to check levels).

Butane gas is flammable and can cause eye problems, so you should wear glasses/safety goggles whenever the presence of the gas is expected. Since we will be re-using the OEM butane cartridges, it is very important to make sure the cartridges are EMPTY. Depress the brass valve on the top of the cartridges until all pressure is released (no sound is heard). Make sure there are no open flames near by.

The Thermacell Hack demonstrates the first method. I used this method for about a month and found it works reasonably well and it is easy to remove the check valve. The problems are that it is slower to refill and the refill can tip has to modified (which usually makes the tip easier to break when using). This can be troublesome when in the back-country you need to refill and someone breaks the only butane refill tip you have with you (actually happened).

The rest of this step explains how to install an in-let butane refill valve. I’ve seen videos and read articles on how others have used plastic valves from disposable lighters and such. I prefer regular metal in-let butane refill valves because they are easier & quicker to “harvest” and install. Buying a valve costs almost double of what it costs to “harvest” a valve ($8 compared to $5).

There are a couple of YouTube videos on how to “harvest” metal valves from Harbor Freight Tools pencil torches. The valves from Harbor Freight are Ronson style valves, so extracting them can be difficult without creating your own tool or purchasing a specialized tool for the job (figure 10 above shows the Gas Valve Installation Tool. Another problem with the Ronson style valve is that the tip is exposed rather than recessed (refer to figure 9). I found a better valve for the purpose at the local Menards (Tool Shop 242-999 Pencil Torch) for under $5. (Figures 5-9 compare the Tool Shop/Harbor Freight pencil torches/valves.)

Installing the in-let valve is fairly easy:

1. To remove valve from a Tool Shop 242-999 Pencil Torch use a ¼” slotted screwdriver. The valve tip will be slightly pressed in by the screwdriver when removing.

2. Drill a 13/64" hole in the bottom center of the bottle (figure 11). This will dislodge a small metal ball. Remove the ball using a magnet with a smaller drill bit. Insert through the hole and shake container lightly until the metal ball sticks to the smaller drill bit and then pull it out (figure 12).

3. Press the in-let valve into the hole and screw valve in until it stops at the “O” ring (figures 13-14). Figure 15 shows that the valve tip is flush to the bottom and not exposed to accidental release of butane.

4. Mix up some 2-part epoxy and dab around the outside edge of the valve making sure none gets in the valve (figures 16-18). I have used the valves with and without the epoxy with no problem, but I still prefer using the epoxy as extra “insurance” (no leaks).

5. Let the epoxy sit for 1 day and add fuel up to the mark around the container. Check the level the next day to be sure the cartridge doesn't leak. When filling, you may need to fill a bit, depress valve to release some of the gas pressure, and then finish filling upto the line.

Step 2: Re-coating the Repellant Mats

Tools & materials needed

- Insect repellent for horses (Celebration Spot-On)

- Rubber, Latex, Nitrile, etc. gloves

- Medicine dosage syringe (most pharmacies)

- 2 oz. spray/atomizer bottle (Walmart travel section)

- Blue food coloring

- Disposable pill zip lock bags (most pharmacies)

There are numerous DIY videos on YouTube showing how to re-coat the used OEM mats. What’s interesting is all of those I watched used various dilutions of 10% permethrin – usually diluted 1-5, resulting in 2% coating on the mats. The videos mention that the coatings seem to work, yet none that I’ve watched mentioned how effective the results were. The OEM mats use 21.97% allethrin, so it would seem better to use a similar concentration when re-coating. I chose to use is the concentration used for horses. I found mine locally at a Tractor Supply Company (TSC) store. The product, Celebration Spot-On (figure 2), has a 45% concentration of permethrin. I use it diluted 1:1, so the mixture is approximately the same concentration as the OEM.

Caution: Permethrin in liquid form is toxic to small pets, especially cats & aquatic animals, so be sure to let any unused liquid dry completely before disposing of. I recommend using disposable gloves when handling liquids during the re-coating process. Please read and follow precautions on the Celebration Spot-On before handing.

Before doing the actual re-coating, test the 2 oz spray atomizer bottle with water to check how the spray will look when sprayed on paper. A “spritz” type spray pattern (almost wet droplets pattern) works better than a fine spray pattern. If the atomizer produces a fine spray, then take a pin/safety pin and push into the nozzle a bit and re-check until you get the desired result. When sprayed, the results can be then be spread more evenly over the mat surface.

Here is the process I used:

1. Place one dose of the Celebration Spot-On into a 2 oz spray atomizer bottle (figure 3)

2. Add an equal amount of water using a medicine dosage syringe (figure 4)

3. Add twenty drops of blue food coloring (figures 5 & 6). Besides coating the mats with a blue color again, the color makes it easier to get a more uniform coating on the mats.

4. Place the white side of the old mats upward on disposable paper

5. Spray the diluted solution onto the white surface of the mats (figure 7). Note: I only re-coat the white sides of the mats.

6. After the mats have dried, I place each of them in disposable pill zip lock bags (figure 8) and store in a dark place away from UV light.

Note: I did not expect the food dye to mimic the change in color like the OEM mats, but surprisingly it did change somewhat. Figure 9 shows a used OEM mat after it gave out (5 hours). The re-coated mat is shown in the middle after it finally gave out (a little over 6 hours) – some the food coloring remains. A mat that was re-coated at the same time as the one in the middle is shown for comparison.

Step 3: DIY Thermacell Stand

Tools & materials needed

- 37½ ” piece of 9 gauge wire (such as tension wire used for chain link fences)

- (2) 8 mm bolt thread caps

When hunting, I just hang the Thermacell on anything convenient. When on the back deck, I don’t like to just leave the Thermacell on the table since it sometimes gets in the way. I couldn’t find anything to use as a support/stand for my Thermacell, so I decided to make one myself. This stand is made from a single piece of 9- gauge wire (5/32”) that I had available. I put 8 mm bolt thread caps on the ends to cover any sharp ends of the wire.

Figure 1 & 2 show how the Thermacell holster hangs on the stand. Figures 3 & 4 show the stand from different angles. Figure 5 provides the bend measurements. The stand is light weight and takes up minimal space on the deck table.

Here is a step by step guide:

1-Cut a 37½” piece of 9-gauage wire. Make marks for the bends at the following lengths:

1¼” (“D”), 4” ("C”), 10½” (“B"), 15½” (“A”), 22” (“A”), 27” (“B”), 33½” (“C”), and 36¼” (“D”)

2-The bends at “A” should be done in two steps. Make the first bends 90 degrees. The wire should lie flat on on a table top after both bends have been made.

3-Next make 90 degree bends at “B”. Theses should be perpendicular & vertical to the table surface.

4-Now complete the bends at “A” until the vertical lengths are parallel at “B”.

5-Next make the bends at “C”. The bends should be parallel to the table top and angled slightly less than those of the base at “B”.

6-Make bends at “D” until they are perpendicular to the wire between “A” points shown in figure 5.

7-Put screw protector caps on ends of wire

Step 4: Installing a Fuel Level Label

Tools & materials needed

- Computer & printer

- Label material such as Avery 8160 or Avery 5160

- Clear packing tape

- Scissors

One of the things I added on my Thermacells are fuel labels showing the hours remaining. Figures 1, 2 & 4 show the front and backs of one of my Thermacells. Figure 3 shows a closeup of the label. The last photo is a copy of the label that you can download and print your own fuel labels.

To use

1-Download the label photo

2-Insert photo using your favorite label software (I used Avery 8160 address label sheets)

3-Size the photo so that the distance between the zero and “12 hr” markings is 2”


5-Cover the printed label with clear packing tape to protect it from the elements

6-Cut out the section between “4 hr” and “12 hr” and place on Thermacell (refer to figure 3 for placement)

Step 5: How to Make Viewing of Fuel Levels Easier

Tools & materials needed

- Flashlight

In bright sunlight, at dawn and at dusk, it is very hard to read the amount of fuel remaining in the fuel window. Something I have done to remedy this problem for me is to leave the cover for the butane bottle off when putting the Thermacell back in the holster (see figure 2).

When I want to check the fuel level I place my flashlight in the small indentation left by the butane cover (figure 3 & 4) and check the fuel level on the back.

Bright sunlight

-Figure 5 shows the fuel window as it normally appears; figure 6 shows the fuel window using a flashlight (low fuel level).

-Figure 7 shows the fuel window as it normally appears; figure 8 shows the fuel window using a flashlight (higher fuel level).


-Figure 9 shows the fuel window as it normally appears; figure 10 shows the fuel window using a flashlight (higher fuel level).

Step 6: Make a Mat Holder Insert for the Thermacell Holster Pocket

Tools & materials needed

- Travel Band-Aid pack

- ¾” tape

- scissors

- 1½“ x 4¾“ piece of black material (hard rubber or plastic)

The latest version of the Thermacell holster has elastic at the top of each pockets. Typically, I put a spare butane bottle in one pocket and put spare mats in the other.

When the butane or the repellent mat needs replacing on the Thermacell, you need to be able to change either one fairly fast because the bugs are about to become a real problem!

Getting the butane bottle out of the pocket is usually not a problem. Getting out a replacement repellant mat can be very difficult.

This is my solution to that problem:

1-Started with a travel Band-Aid packet (figure 2)

2-Cut the packet at the “hinge” and kept the top half (cover) that has the label

3-Trim excess plastic around the cover and remove the label

4-Cut a section of hard rubber or plastic (black) to fit the Band-Aid cover (1½“ x 4¾“)

5-Attach both together using black ¾” tape (figure 3 & 6) almost to the top ends of both.

Up to three OEM or three re-coated mats will easily fit in the mat holder. The mat holder is then inserted into a pocket with the white side facing inward (figure 1). Inserting the mat holder in this direction allows a finger to easily slip behind & grip the holder; the black rubber on the outside blends in with the Thermacell holster color (figure 1). Now, when I need a replacement mat I pull the mat holder up about half way, partially open the mat holder, pull out a mat and push the mat holder back down. Fast and easy!