The Thermacell C-4 fuel cartridge refill effectively repels mosquitoes for up to 48 hours by creating a 4.5 meter zone of protection when used with Thermacell devices and Thermacell Repellent Mats. Use this fuel-only refills for when you have spare Thermacell repellent mats. Heat produced by a Thermacell Fuel Cartridge is directed to a small mat infused with the repellent allethrin, a synthetic version of a naturally occurring repellent found in chrysanthemum flowers. For best results, use on days with light or no wind (bugs are at their worst on these days), and allow 10-15 minutes to form a complete zone of protection around the unit
