The Thermacell Earth Scent refill pack will keep hunter's mosquito-free with Earth Scent cover for hours in a 15x15 ft. comfort zone. Repellent mats with Earth scent emit allethrin and the smell of musky dirt and decaying leaves to repel mosquitoes and mask human odors. Each mat is effective for up to four hours. Each butane cartridge will operate the unit for up to 12 hours.