A hot surface igniter kit (HSI kit) is a component used in gas‑fired furnaces, boilers or other heating appliances. It replaces the traditional pilot‑flame or spark ignition system by heating a ceramic or silicon‑based element until it becomes red‑hot, and thereby igniting the main burner gas. The “kit” portion implies the unit includes a heating element (igniter), wires or leads, mounting bracket/hardware, and often terminals/connectors.

Such kits are commonly used for field replacement of burnt‑out or failed igniters. Examples from manufacturers show the kit often replaces dozens of older part numbers across many equipment models