Include: 1 pc P323664 furnace vent safety switch 250F Manual Reset Compatible Models: 5001521A, 5001522A, 6501521A, and 650122A Enhanced Safety: Monitors the venting system to prevent potential overheating and ensure safe, reliable furnace operation Durability: Built to withstand regular use in various heating conditions, providing a long-lasting solution for vent safety management Fuel Compatibility: Supports both liquid propane and natural gas models, providing versatility in fuel options The P323664 vent safety switch is a critical component designed for Williams Enclosed Front Vented Room Heaters. This safety switch plays a critical role in monitoring the venting system, helping to prevent overheating and ensuring safe operation of your furnace. It is compatible with both liquid propane (LP) and natural gas (NG) models.