There have been 27 neighbor complaints of the black mold and seven odor complaints since last year, the air district wrote in the letter.
The vapors "accumulate inside aging warehouses, and are eventually emitted into the ambient air and across property boundaries," the Sept. 7 violation letter to Diageo said. The company, which owns owns popular brands Crown Royal, Smirnoff and Bushmills, has until Nov. 3 to come up with a compliance plan.
Diageo is one of five bourbon-making defendants in lawsuits filed in June that blame storage warehouses in Louisville and Frankfort for causing the black fungus to gather on properties. The suits name some of Kentucky's most famous bourbon producers, including Jim Beam; Brown-Forman, which produces Woodford Reserve; Heaven Hill and Buffalo Trace. The suits say the black fungus causes property damage.
The air district said it has found that the sooty substance resembles baudoinia, a fungus that grows rapidly in ethanol-rich environments. The violation letters say Diageo could face fines of up to $10,000 a day if it does not comply.
"Our goal is to get them to come up with a control plan to stop this," Nord said.
Nord declined to comment on whether other bourbon makers will be receiving similar violation letters.