Oil refining is a dynamic process and requires extensive monitoring and pressure control within the system. When operating conditions change flares may be used as part of the process to ensure that refinery equipment is operated safely. In most circumstances, the hydrocarbons are recovered and reused in the refining process. However, in some cases residual hydrocarbons are burned off. The flares turn hydrocarbon vapors into harmless water vapor and carbon dioxide. This is the most environmentally sound method of preventing hydrocarbon vapors from escaping into the atmosphere.