Placed pizza stone in 525f oven to preheat. Smoke pouring out. Opened window, exhaust & even the bathroom exhaust. Thought it would quit eventually. Put pizza in oven for approx 8 min. Smoke still billowing... removed pizza with stone. Stone as black as charcoal. Inside of oven, including window on door, soot coated everything. Pizza turned out great! Read on Pinterest & other sights, to put stone in oven on self cleaning cycle would work. Was going to shower when I saw blue flames through the oven door. The damn stone was on fire! Shut the self cleaning cycle off. Scared the crap out of me! What happened?