DALLAS (CBSDFW.COM) – A Dallas utilities contractor faces more than $420,000 in fines and possibly further penalties following the death of a worker after exposure to dangerous levels of gas.

The U.S. Department of Labor on Friday cited RKM Utility Services Inc. for “failing to protect workers” when an employee died after exposure to dangerous levels of hydrogen sulfide while working in a trench in Dallas.

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Inspections done by the department’s Occupational Safety and Health Administration (OSHA) determined that the company failed to train employees on the health hazards of the gas and had exposed other employees to these dangerous levels.

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The company could be fined at least $422,006.

The department said hydrogen sulfide is typically found in places like trenches and sewers and is flammable and toxic. Employers are required to train workers on the hazards of the gas, provide the proper safety equipment and test the air for the gas.

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According to the department, the company has 15 business days to comply to the safety and health citations.