In what scenario is purging the furnace especially important?

Purging the furnace is particularly critical after any flame interruption. This scenario usually involves a situation where the flame has gone out due to various reasons such as fuel supply issues, air supply problems, or unexpected disturbances. When this occurs, unburned fuel can accumulate in the combustion chamber. Before attempting to reignite the burner, purging the system helps to safely remove any residual fuel gas from the furnace, which is crucial for preventing potential explosions or flashbacks. Ensuring that the combustion chamber is clear of flammable gases is a vital safety precaution that minimizes risks associated with starting combustion processes after any flame interruption.