The study of fire in the process industries has displayed significant potential for further research in the oil and gas business. The possibility for the occurrence of fire incidents due to the vaporization of hydrocarbon components above the wastewater flowing through a refinery's drain was studied. The liquid sample contains mixture of hydrocarbon products and water, which underwent the distillation process to extract oil and remove water contents. There were 77 hydrocarbon components ranging from C9 to C22. The mole fractions of the components in the liquid phase were obtained from the GC results, while the mole fractions of the components in the gas phase were calculated according to Raoult's law. The lower flammability limits (LFL) and upper flammability limits (UFL) for each mixture component were calculated using stoichiometric concentration method. The LFL and UFL for the mixture were calculated with accordance to Le Chatelier equations. Some waste generated by the refineries can be dangerous and generate flammable mixtures, which can cause fire. The results can give some method and guidelines to those who are involved in the relevant fields. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011).