Takata uses the chemical ammonium nitrate to create a small explosion and fill air bags quickly in a crash. But the chemical can deteriorate when exposed to high humidity and temperatures and burn too fast, blowing apart a metal canister. That can hurl hot shrapnel into unsuspecting drivers and passengers. Scroll down to continue reading Trending headlines DOWNLOAD OUR FREE NEWS APP At least 20 people have been killed worldwide and more than 180 injured. The latest recalls are part of the largest series of automotive recalls in U.S. history, with 19 automakers having to recall up to 69 million inflators in 42 million vehicles. The problem brought a criminal conviction and fine against Takata and forced the Japanese company into bankruptcy protection. The recalls, which are being managed by NHTSA, are being phased in over the next three years. Older models and those in states with high humidity and temperatures are getting priority. Many automakers have been slow to replace the potentially deadly inflators.