The department was dispatched to Hawthorne alongside a Tower Ladder from Thornwood to a report of an explosion at 19 Bradhurst Avenue. First arriving units were getting reports of smoke coming from the North side of the building. Interior crews checked the MRI area, where the explosion was reported, while TL49 sent a crew to the roof. It was determined that one of the MRI machines malfunctioned which caused the system to neutralize the magnetic field by dumping helium. The helium was vented out through the roof unit which was the “smoke” that bystanders reported. Interior and roof checks were ok and units were released by command soon after.