Dorothy Dougherty, director of standards guidance at the agency, said there is no date set for when regulations would be drafted.
"We have to take our time," she said.
Most of the comments cautioned against applying too strict of a standard to every industry, from food processing to sand blasting to coal dust at neighborhood print shops.
"If I spill a gallon of gas in the middle of this room, we're all going to head for the exists. It I drop a bag of flour, we aren't," said Thomas Lawrence of RRS/Schrimer of Ballwin, Mo..
Cost estimates for compliance ranged from $2,000 to test dust for combustibility to as much as $30 million to upgrade a power plant.
Brian Edwards of Tucker, Ga.-based Conversion Technology warned that many costs are the same for specific machinery regardless of business size.
"If a company has to put in explosion-suppression equipment, it's going to cost the same whether it's a Fortune 100 company or a mom-and-pop shop, and that's hundreds of thousands of dollars," he said.