I was a MM3 worked in AC&R shop HVAC and cleaner of the air filters. I was also on the fire department full time for a total of 9 months went from being an OBA Investigator to One on One. I saw what a storeroom fire could do in the way of heat transfer deck to deck bulkhead to bulkhead before on my ship. My guess is they had a flash fire in laundry {Lint} and it went from there. It likely didn’t take 30 hours unless you count reflash watch time. Even at circle William or William the ducts can still burn dust. It sounds like they were very lucky.
How many laundry rooms does an aircraft carrier have? Is this the only one? I suspect it is toast and all of those machines will need to be replaced.