TRAVIS LOLLERNASHVILLE, Tenn. (AP) â¿¿ New safety rules will not be approved any time soon even though they could prevent accidents like the ones last year at a Tennessee metal powders plant, where fireballs fueled by iron dust contributed to five deaths. The Occupational Health and Safety Administration is developing rules that would require many industries to better control combustible dust hazards. The rules were recently moved to a long-term agenda, despite pleas from the Chemical Safety Board to put them on the fast track. The Chemical Safety Board investigated accidents Hoeganaes Corp., a plant near Nashville, where five people died a year ago. "Hoeganaes should have made a believer out of everybody. It's appalling what went on there," said Bill Kauffman, a retired professor of aeronautical engineering with the University of Michigan. Kauffman helped develop rules in the 1980s that have led to a steep decline in deaths from grain dust explosions and was an expert on a panel last May that discussed crafting the new regulations. He believes some officials at OSHA are trying to make them too complicated. "They seem to be splitting hairs â¿¿ 'This dust. That dust.' â¿¿ Why don't they just say 'Anything that burns?'" he said. OSHA spokeswoman Diana Petterson did not offer much explanation. She said the agency continues to develop the rules, and preventing worker injuries and deaths remains a priority. She would not discuss the matter further. Combustible dust is the technical term for any dust that will catch fire, and most will if it is ground finely enough â¿¿ including dust from chemicals, plastics, metals and foods. The Chemical Safety Board has been studying the hazards of combustible dust since a series of deadly fires and explosions in 2003. "We really don't know why OSHA is doing this," said Rafael Moure-Eraso, chairman of the Chemical Safety Board. "We do know that workers keep dying."