What may be the result of igniting a greater than normal amount of combustible mixture?

Igniting a greater than normal amount of combustible mixture can lead to a puff-back. A puff-back is a small explosion that occurs when there is a sudden ignition of unburned fuel within the combustion chamber, resulting in a pressure wave that pushes exhaust gases back through the system. This usually happens when there is an excessive accumulation of combustible gases that ignite all at once, causing a rapid release of energy.

In the context of combustion systems, if the air-to-fuel mixture is not properly balanced or if ignition occurs while there is an improper amount of fuel or air, it can lead to this backfire phenomenon, where the pressure suddenly changes and pushes out gases. This is particularly important in systems where there is buildup or leaks of combustible gases, as it can cause safety hazards and system damage.

Other choices do not directly stem from merely igniting too much combustible mixture. A rapid boiler warm-up pertains to the speed of heating in a boiler, which is a different aspect of operation. Negative furnace pressure involves airflow issues within a combustion system and is not a direct result of igniting an excessive mixture. A boiler explosion, while serious and damaging, is typically associated with other catastrophic failures like mechanical failure or water level issues rather than the ignition of combustible mixtures