The concept is that the hydrate concentrates gas by a factor of about 164, without the cost of compressing and transporting gas at high pressure. In shipping, preservation of hydrated gas is vital to prevent losses. The cause for this anomalous hydrate self-preservation effect is most likely uncertain because of an outer ice barrier that prevents inner-particle dissociation. The ice protective shell happens because the water from the melted hydrate surface, caused by endothermic hydrate melting, freezes. Laboratory measurements and calculations indicated that hydrated-gas transportation is economical for distances that are greater than approximately 400 km. British Gas Ltd. has a pilot facility to convert gas to hydrate.