They do believe me I know I was a nozzle-man. They have the drills so you are ready. The drill doesn't prevent the fire though. Safety walk throughs do sometimes but still not always.
I'll give you an idea of a possibility. The vacuum cleaner may have had some issues in the motor winding and went unnoticed as it was put away. After being stowed it smolders and ignites the motor housing. The motor housing burns and other things begin to catch fire. Here is where it gets difficult and dangerous. If the compartment was air tight or close to it a good size fire could erupt then die down to a large smolder. It might even go unnoticed but in the mean time heat from inside that compartment transferred to the next compartment through the walls. I've seen it happen before two decks above a fire and another fire erupts.
Finally someone smells smoke. When you smell smoke on a ship you call Fire and then try to locate the space. You do not simply go opening doors. You place the back of your hand on the hatch or door. If it's hot your hand feels it and jerks away from the heat. You do not open that hatch or door until a hose team is suited up and the nozzles spraying or ready to spray. The sudden influx of oxygen into an oxygen starved fire can mean a serious flash happens. The fire literally goes from smoldering to hell in seconds in those conditions.
You have to always keep in the back of your mind that you do not know the oxygen level of any given space in a fire. For that reason after a fire is put out you still are in a fire fighting posture until that space has been checked for oxygen and explosive gas and the fire is overhauled.
It seems we found a design flaw in the construction of the ship. The overflow vent for the contaminated AVGAS tank was in the main engine room. It was SUPPOSED to overflow into the bilges to be pumped overseas while underway. BUT it was over the main engine. On this day, it overflowed and rained AVGAS on to the main engine. Huge fire. Dead in the water for several hours. Smoke throughout the whole ship before the ventilation system was shut down. Very scary time. Had to go back to Sasebo for repairs when limited power was finally restored.
Where liberty dwells, there is my country." Benjamin Franklin