Intentional releases happen primarily for safety reasons if needed to vent pressure, or during start-up or wind-down of production. Most intentionally released methane is burnt on release (flaring) and converted to C02, usually because the production site is too far away from a major demand centre to make transporting and selling the gas unattractive. Large but poorly quantified amounts of methane also escape through leakage from downstream distribution networks, as well as from refineries and various methane-consuming industries.