CHICAGO (WBBM) – Air sampling gets under way in earnest Tuesday in an attempt to determine what–if anything–Metra can do to trim emissions of potentially harmful diesel soot that accumulate in its two major downtown terminals and in trains that are leaving them.

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Metra officials hope to have preliminary results from the study, by Chicago-based Carnow, Conibear & Associates, within a month.

Independent testing done by a Chicago Tribune reporter found that trains pulling out of Chicago Union Station and Ogilvie Transportation Center can have air trapped inside passenger cars that contains levels of diesel soot up to 72 times higher than on neighboring streets.

At stations, levels were highest on platforms and in adjacent terminal areas of Amtrak-owned Chicago Union Station and at Ogilvie Transportation Center.

Metra last week formed a task force on diesel soot emissions that includes representatives of the U.S. Environmental Protection Agency, the Federal Railroad Administration, the U.S. Occupational Safety and Health Administration, U.S. Sen. Dick Durbin (D-Ill.), Amtrak and the buildings that tower above Union Station’s terminal trackage, each of which is required to maintain exhaust fans.

Metra Acting Executive Director Bill Tupper said he wants the consultants to determine if Metra can make changes in filtration systems or take other steps to mitigate the soot, or determine if the only answer is new locomotives.

Tupper said last week that work has been performed or is scheduled on the majority of Metra’s locomotive fleet to bring the locomotives up to existing federal standards. But he said no locomotive built today can meet standards projected for 2015.