Though a program displays panels showing all the critical processes of a real rig (fire and gas detectors, valve status, oil flow from the sea bed and so on), and then responds to the actions of the trainee by altering these displays appropriately, a human operator can intervene at any time if things seem to be going too smoothly.

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"The absence of the valve and regulator would explain how such a large volume of gas would be released into the home, " Curry told CNN.

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Mike Schaffner directs information technology for the Valve and Measurement Group of oil and gas products and services company Cameron in Houston.

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In other energy news, Federal Reserve Chairman Alan Greenspan told Congress yesterday that shrinking supplies of U.S. natural gas mean the nation must build more gas import terminals to create a "safety valve" that will help stabilize prices.

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