Do mosquito coils really work? And are they bad for your ...- Cox Set Mozzie Coils ,Mosquito coils work in one of two ways. Those that contain insecticides will kill (or at least "knock down") mosquitoes while those that contain aromatic substances (such as citronella) will repel ...The Best Mosquito Coils and Mosquito Rings | INSECT COPReview. AllTopBargains Mosquito Repellent Coils work just like any other mosquito coil. You set them up in the wanted spot and light them up. These mosquito coils last for 5 to 7 hours and repel not only mosquitoes but will also scare away other small flying insects that might bother you.