An explosion at a Wanhua Chemical plant in Yantai, China, killed four people and injured another four. Wanhua, a producer of polyurethane raw materials and other industrial chemicals, is still analyzing the cause of the explosion. According to an article from the American Chemical Society’s Chemical & Engineering News, the company says its preliminary investigation indicates that it occurred in a crude methylene diphenyl diisocyanate (MDI) purification tank that, at the time, was holding the material at pressure and temperature levels within its design specifications.

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