Final answer:
A safety shut-off device on an oil burner is a mechanism that detects excessive smoke or improper fire and shuts down the burner to prevent hazards and improve efficiency.
Step-by-step explanation:
A safety shut-off device, often referred to as a smoke detector or smoke alarm on a heating system, is a device mounted on the smoke stack or chimney that will shut down an oil burner if there is excessive smoke or if the fire is improper. This is an important safety feature as it prevents the buildup of smoke, which can be hazardous to health and safety, and also ensures the oil burner operates efficiently. The safety shut-off is triggered by sensors that detect smoke density or irregular flame patterns, thereby activating a mechanism to halt the fuel supply to the burner and stopping the operation.