LOS ANGELES — Post Holdings, Inc. and Ralcorp Holdings Inc. have reached a settlement with the Environmental Protection Agency to pay $635,000 for violations of the federal Clean Air Act, including failing to install required air pollution controls at the company’s cereal production facility located in Modesto, Calif. The penalty is in addition to approximately $1.4 million the company already has spent on equipment necessary to reduce emissions.

“Like many large manufacturers, Post operates multiple plants across the nation, and ensuring that they have proper air pollution controls in place is critical,” said Jared Blumenfeld, regional administrator for the Pacific Southwest at the E.P.A. “Our goal is to protect the public from harmful ozone and particulate.” 

The E.P.A. said its federal investigators found certain types of equipment at the facility, such as cereal coaters and dryers, were emitting volatile organic compounds (VOCs) without required pollution-reducing controls. The E.P.A. also said it found the facility did not have all required operating permits.

Post originally spent $1.4 million in 2012 on the installation and operation of equipment that captures and controls emissions, reducing VOCs from the facility’s operations line by 95%. The most recent settlement also requires the facility to monitor emissions and provide quarterly reports to the E.P.A.

“Post is committed to compliance with all environmental laws and regulations,” the company said.