Thermacell, mosquito repellent appliance, operates on a small butane cartridge which heats a repellent pad, emits an odorless vapor that creates a cell of protection for up to 12 hours in a 225 sqft area, epa approved, for refill cartridge use TV #876557. Mosquito Repellent Refills work in ALL Thermacell repellers, lanterns and torches