Wasps, Mud Daubers, Birds And Rodents Pose A Serious Threat To The Furnace On Your RV. They Can Enter Through The Furnace Vents And Cause Serious Damage By Building Nests That Interfere With Air Flow. Camco (Model FUR 500) Flying Insect RV Furnace Screen Fits Atwood Hydroflame Furnaces That Do Not Have Access Door. As Camco Offers Several Furnace Screens, Consult Size And Photos To Confirm This Screen Will Fit Your Furnace Vent. This Easy-To-Install Screen Will Help Ensure That Your Furnace Vent Stays Free From Costly Invasion By Unwanted Pests.