What does purging a furnace involve?

Purging a furnace involves forcing air through it to eliminate any combustible gases or vapors before ignition. This is a critical safety procedure designed to prevent the risk of explosion or backfire when the furnace is started or restarted. The process ensures that any unburned fuel that may have accumulated inside the furnace chamber is removed, creating a safe environment for combustion.

During purging, fresh air is introduced to facilitate the dilution and dispersion of these potentially hazardous gases. This procedure is essential to maintain the safe and efficient operation of a furnace, particularly in situations where there may have been a disruption in the fuel supply or when maintenance has been conducted.

The other options, while related to furnace maintenance and operation, do not accurately describe the purging process. For instance, removing all fuel from the furnace may be part of a shutdown or cleaning process, but it does not specifically pertain to purging. Cooling down the furnace and cleaning the furnace interior are also important tasks in maintenance but do not define the purging action, which is primarily about air movement for safety.