Repels mosquitoes that may transmit zika virus. For Outdoor Use: Each coil burns for 5-7 hours. Outdoors place one coil every 10 feet. Use on patios and porches. Dependable insect control since 1953. PIC Mosquito Repelling Coils helps to repel mosquitoes in confined areas outdoors. It is useful in places where there is little or no breeze such as patios and porches.