Abstract: On April 6, 1994, Employee #1, Employee #2 and coworkers responded to a leak coming from the mechanical seal of the heavy gas oil pump of Coker Unit Number One. They placed water and steam on the leak to suppress the vapor coming from the seal. It was decided to shut down the pump and transfer the product to secondary pump. As the primary pump was shut down, the mechanical seal blew causing a vapor cloud to generate from the seal. They continued to put steam and water on the seal and isolated the pump from the pipeline. The remaining product in the pipeline leading to the primary heavy gas pump vaporized leading to the dispersions of vapor clouds. Employee #1 and Employee #2 were taken to Long Beach Memorial Hospital and treated for inhalation of hydrocarbons.