Increasingly stringent regulations around the world have caused refiners to review their current refinery opera-tions and search for methods to comply with such regulations. An example of this is the United States Environmental Protection Agency (US EPA) standard1 for the depressurisa-tion of a coke drum to a closed blowdown system during the decoking cycle. According to this regulation, the pressure of the coke drum is to be lowered to 2 psig or less before vent-ing the drum to the atmosphere at the end of the cooling step. This will result in a lower pressure difference between the coke drum and the atmosphere right before venting, leading to fewer volatile organic compounds (VOC) emis-sions and quieter openings of the coke drum vent valves.