On a clear, calm Monday evening (January 18, 1999), a tanker truck carrying 22 tons of liquid anhydrous ammonia rolled over as it was making a sharp turn outside the Farmland Industries chemical plant in Pollock, Louisiana. The liquid ammonia escaped through a valve. Assume that it formed a 2500-m2 pool and turned into gas as it went into the air. Estimate the concentration of ammonia vapor 500 m from the accident. Is the concentration dangerous to the workers in the plant? The wind speed during the period was nominal (3 m/s).