A flare is an important safety device for control and disposal of combustible gases. They are designed in accordance with API, ASME, EPA, and other codes. However, many other details and possible oversights, not found in the recommended practices, standards, and codes, can lead to dangerous conditions-bottlenecks, equipment malfunction, overpressure, flameout, vapor clouds, liquid carryover (burning rain), internal burning, and explosions. These normally overlooked details are also covered in this article. Vents and vent stacks will also be reviewed since they are simply a flare without a flame. They also use much of the same technology as a flare, except for the pilots, ignitors, and flame retainers. Some of these unsafe conditions, their causes, and their initial warning signs are presented from actual field experience and discussed in order to educate the engineer (design, piping, process, operating), plant operators, and maintenance people. (C) 2006 American Institute of Chemical Engineers.