One of the most alarming trends we see when guarding furnace intake and exhaust vents is the use of vent screen mesh discs, which are simply wire screens that have been cut to form-fit inside vent terminations. The vast majority of these screens fail to meet minimum NFPA (National Fire Protection Association) airflow standards for safe use during winter. Since combustion produces carbon monoxide, maintaining a high rate of airflow is why we also advocate extreme caution when using any vent screen. Mesh discs are known to deprive furnaces of their energy efficiency, reduce component life by placing the furnace’s draft inducer motor under unnecessary load and potentially creating safety hazards that may trigger furnace lockouts. There are additional problems with mesh discs, including their inability to protect vent terminations, which we will describe in detail below.

Weak and Low Grade Steel Mesh Discs Fail Quickly

Mesh discs typically are very weak since they are not supported by a housing, and bend to conform to the hub, which makes them very easy to dislodge and push in by animals. Additionally, as one of the cheapest options to guard furnace intake and exhaust vents, the wire mesh is commonly made of low quality steel which will rust and eventually fail. In the picture to the left, the vent screen disc exhibits both of the aforementioned concerns. The screen has rusted, permanently staining the white PVC vent termination, and it has been easily pushed in by an animal. Fortunately this screen was retrieved with a length of wire with a small hook on the end. In some cases an animal will flip the disc to get around it or drive the entire disc right into the Furnace’s burner compartment (intake) or into the draft inducer motor (exhaust). Should the screen come into contact with components inside the draft inducer motor, the motor may become severely damaged and require replacement at a base cost of $500.

Replacing Mesh Discs with a Durable Furnace Vent Screen

The preferred replacement for vent screen mesh discs are PVS-RS series vent screen inserts as pictured to the right. PVS-RS series rodent screens are available in 2″, 3″ and 4″ models to fit inside most common vent termination hubs. Not only are PVS-RS series vent screens made with high grade 316 stainless steel wire mesh to prevent rusting, but their anti-corrosive 6061-T6 aluminum housings also facilitate heat transfer which is beneficial for furnace exhaust vents during sub-freezing temperatures and throughout winter. Additionally, the 90% airflow rating of PVS-RS series vent screens exceeds the minimum airflow requirements set forth by the NFPA for use throughout winter while also maintaining superior flow velocity. Since rodent screens do not guard furnace vents from bees, wasps and other insects in the warmer months, PVS-IS series insect screen inserts are also available in our store for use during spring, summer and early fall.

Why Do Some HVAC Technicians Install Mesh Discs?

Unfortunately we’ve seen HVAC technicians installing vent screen mesh discs on newly installed furnaces and have replaced them ourselves while they were still on location. To the left is what a HVAC technician installed vent screen mesh disc looks like just after a month of use. If not replaced, this vent screen will continue to rust until it fails. Should failure occur, the screen may fall to the ground and pose a hazard to those who may step on it. In some cases the screen will fall into the pipe and may require the vent pipe be severed to gain access to the screen before it finds its way into the burner compartment or draft inducer motor.

In many cases, HVAC technicians will not install vent screens on furnace intake and exhaust terminations unless the customer requests it. When technicians do install screens, some may use mesh discs as they are cheap and often fail after a newly installed furnace’s labor warranty expires. Additionally, degradation in the appliance’s performance and energy efficiency won’t be known to most consumers so long as their furnace operates.

Removing Vent Screen Mesh Discs Before Problems Arise

Fortunately removing mesh screen discs from a furnace’s intake and exhaust vent, before problems occur, is simple. With a pair of needle nose pliers, the disc can be removed and discarded so the appropriate PVS-RS or PVS-IS series vent screen may be installed inside the hub. The removal process is detailed, with video, on our cheap vent screen replacement page. However, it’s best to have a replacement screen ready to install before removing the existing screen. You may visit our PVC vent hub inserts sizing page for help in determining the size of your vent termination so the appropriate vent screen may be purchased and received before removing the existing mesh screen disc.

Requesting Additional Assistance

We hope the information on this page will help you avoid the pitfalls of using mesh discs inside your furnace’s intake and exhaust vent terminations. Should you need additional help, don’t hesitate to contact us with any specific questions or concerns you may have.