Hot surface igniters take a lot of abuse in a furnace. Every time a call for heat comes, the igniter glows red hot then cools down. The igniter is a common component that fails when the furnace is running frequenctly, such as during the winter.

When an igniter fails, it is usually due to a crack  around the hottest part of the igniter. A sign that an igniter is about to fail, is the appearance of a white chalky residue on it. This chalky residue is the result of extreme heat over time. When inspecting a hot surface igniter, never touch the gray part of the igniter with your fingers. Only touch or handle the base. The oil from your fingers will create a hot spot on the igniter which mayshorten the life of the igniter.