How to Refill ThermaCell Butane Cartridges

Thermacell butane cartridges are used in mosquito-repellent devices, which use heat from burning butane fuel to activate a chemically treated mat designed to repel mosquitoes. Thermacell uses this technology in lanterns, torches and fans that are portable and designed to repel mosquitoes in a 15-foot radius.

These fuel cartridges are designed to last 12 hours each. However, most customers feel that the butane refills are too expensive for the amount of time for which they function. Since replacement fuel cartridges and repellant mats are usually sold in small packs of individual units, many customers have mentioned the desire to refill Thermacell butane cartridges themselves using bulk butane, which is both cheaper and more environmentally friendly.

Butane is a small, highly flammable hydrocarbon vapor often used as fuel. It's an odorless, colorless substance that exists as a gas in atmospheric conditions, so it's often handled in pressurized cylinders.

However, because it's so flammable, there is always the risk of fire when handling butane. In addition, if butane is inhaled, it can cause drowsiness, unconsciousness and even asphyxia since it quickly enters the bloodstream and depletes the oxygen supply. Since butane is often contained in a small cylinder or container under pressure, the risk of inhalation is serious if the container is disturbed or damaged.

Refilling Thermacell butane cartridges involves modifying the container used to keep butane at a useful pressure. As such, there are hazards involved. Before modifying anything on the cartridge, make sure that it's entirely empty by venting the cartridge into the air in an outdoor location. Vent away from yourself and make sure that you wear safety glasses and protective gloves when doing so.

Depress the valve at the top of the cartridge and listen until all of the pressure inside has been released. If you aren't comfortable working with tools, valves or pressurized gas transfer, weigh these hazards carefully.

There are two ways you can modify Themacell butane cartridges to make them refillable. The first method involves removing a check valve inside the cartridge so that butane can be added. The purpose of a check valve is to control part of the system so that fuel can only flow one way. By removing this check valve, you're making the system refillable.

To do so, you first need to empty the cartridge and carefully remove the brass valve at the end of the cartridge (this is the valve that connects to the Thermacell repellent device). Once the valve has been removed, thread a small, metal screw into the opening to catch the check valve and then use pliers to gently wiggle the screw loose; this should pull out the check valve. You can then reinsert the main valve nozzle into the cartridge. To fill, you'll also have to modify the tip of a butane refill cylinder by slitting the plastic nozzle to create an opening. You should then be able to insert the tip into the cartridge valve to refill the butane cartridge.

The second method involves drilling a hole in the bottom of an empty cartridge and installing an inlet valve into that hole. The opening should then be sealed with epoxy for extra security against leaks. Once installed, you should be able to refill the cartridge directly using the inlet valve. Let any modified cartridge sit for a day or two after refilling in a well-ventilated space so that you can watch the level of butane and make sure there are no leaks.