A greasy dish towel overheated inside a laundry bag at an industrial laundromat Friday night, starting a fire that spread from a drying rack suspended along the ceiling to a folding machine below. Brockton fire officials said there were no employees at Churchill Linen Services on Evans Street when they responded to an alarm around 10:15 p.m. Friday. The building’s sprinkler system managed to confine the flames to a small area before firefighters arrived at the laundromat, located in a large facility near the Campello commuter rail station. Deputy Fire Chief Edward Williams investigated the cause of the fire. “What happens is they wash the product, then they dry the product, then they stick the product in these big bags five feet in diameter that hang from the ceiling,” Williams said. ”