Some firefighters at the scene of a fertilizer plant explosion in Texas were concerned Wednesday night about anhydrous ammonia.

CNN: Explosion hits fertilizer plant north of Waco, Texas

Anhydrous ammonia, a gas used in making fertilizer, can cause severe burns if it combines with water in the body.

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According to the Centers for Disease Control and Prevention, anhydrous ammonia is a pungent gas with suffocating fumes that is used as a fertilizer.

CNN: Explosion hits fertilizer plant north of Waco, Texas

"Anhydrous ammonia will burn but it is unusual for it to detonate, whereas ammonium nitrate has a track record of blowing up, " he told the BBC World Service.

BBC: Texas Waco fertiliser plant blast causes many casualties

"Anhydrous ammonia will burn but it is unusual for it to detonate, whereas ammonium nitrate has a track record of blowing up, " explained Prof Andrea Sella, a chemist at University College London.

BBC: Texas Waco fertiliser plant blast search for survivors

The newspaper said it had seen documents in which the plant said it stored large amounts of anhydrous ammonia, but the worst scenario envisaged was a release of ammonia gas that would harm no-one.

BBC: Texas Waco fertiliser plant blast causes many casualties

Ms. Monforton said she didn't think the West Fertilizer Co. facility that exploded Wednesday night in West, Texas, was "going to be on OSHA's radar screen" because it apparently had few employees, despite the fact that it stored highly combustible anhydrous ammonia.

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What is anhydrous ammonia?

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