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A sheared off valve on an anhydrous ammonia tank at a business in New Hampton, Iowa, forced the evacuation of nearby establishments Tuesday, officials said.

A piece of equipment flew off and struck the valve at Five Star Co-Op at 9:30 a.m. at 16682 245th St. SE, said Cerro Gordo County Chief Deputy David Hepperly.

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The Cartersville Elevator and the Mason City Recycling Center ended up evacuated immediately and several roads in the area remain closed.

Hepperly said Five Star personnel are not able to stop the leak, so they will continue to allow the ammonia to bleed off and monitor the results.

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Anhydrous ammonia is a colorless gas with pungent, suffocating fumes, and is used as an agricultural fertilizer and industrial refrigerant.

As liquid anhydrous ammonia releases from its container into the air, it expands rapidly, forming a large cloud that acts like a heavier-than-air gas for a period of time, according to the Centers for Disease Control. Because the vapors hug the ground initially, the chances for humans to be exposed are greater than with other gases. Symptoms of anhydrous ammonia exposure include eye, nose, and throat irritation, breathing difficulty, wheezing, or chest pain.

“The biggest thing is what the wind direction is right now,” Hepperly said. “We’re lucky enough to have the wind taking it to the south right now where there’s no real effect for anybody.”

No homes in the area ended up evacuated, Hepperly said. “If the wind were to shift to the west, then we would evacuate,” Hepperly said.

Mason City Fire Department is in control at the scene and they and Five Star personnel will continue to monitor the scene, Hepperly said.

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