A PVS-IS2 vent screen at https://pvcventscreens.com/product/pv... was used to replace a recently installed furnace vent screen that already had a wasp nest being built inside of it. The PVS-IS2 vent screen is designed to protect furnace intake and exhaust vents during spring, summer and fall. During winter, when insects are not active, the PVS-RS2 vent screen should be used inside 2" PVC furnace vent terminations having an inside diameter of 2-3/8". When used as intended, the PVS-IS2 and PVS-RS2 vent screens provide complete all-season vent protection to protect vents from bees, wasps, birds, rodents and debris. The PVS-IS3 and PVS-RS3 vent screens are designed to fit inside of 3-1/2" vent terminations, which are also commonly used for residential high efficiency furnaces. For optimal performance, a licensed HVAC technician should inspect your furnace and ventilation system annually.