Abstract: A method for clearing pipework in an oil refinery includes the steps of: blowing, using a first, low velocity gas flow, pipe contents out of the pipework in such fashion that the contents are removed using gas overpressure, to leave a low contents residue; and substantially clearing the residue by a second, high velocity gas flow, the gas flows being such as not to give rise to a hazardous reaction such as fire or explosion. Apparatus for the same includes gas blowing means connectable to the pipework; valving adapted to throttle down an outlet of the pipework, said blowing means and valving being adapted to cooperate to effect both low velocity flow and high velocity flow through the pipework; and gas supply means to the blowing means supplying a gas that will not give rise to a hazardous reaction such as fire or explosion.