An explosion in Midfield on Tuesday sent three people to the hospital. It happened at Hot Metal Coatings on Industrial Park Drive. The victims' injuries were not believed to be life-threatening. Birmingham fire battalion chief Sebastian Carrillo said the mutual aid call came in at 1:58 p.m. "The material that we're dealing with is calcium silicon, which is a material that is used in the pipe-making process," Carrillo said. Firefighters were trying to extinguish the blaze, before it spread to the hazardous material. "There are about 500,000 pounds of this material inside this building," Carrillo said. "It poses an inhalation hazard."