Olive, Thermacell, Mosquito Repeller, Operates On A Small Butane Cartridge Which Heats A Repellent Pad Which 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 #876-557, TV #672-412 Or TV #217-236.