Thousands of Metra and Amtrak passengers come and go on the south platform at Union Station, and breathe the air. Locomotives kick out a lot of exhaust. And if it's not properly vented, it hangs.
Fans are supposed to suck out as much of the exhaust as possible. The owners of the buildings above are required to keep the fans operating.
But Metra and Amtrak say the new owner of the old post office building, which sits atop the south entrance to Union Station, has not kept the fans in good working order.
"Our last inspection at the old post office found five of the 11 fans to be inoperable. And we've let them know that and we can't let that continue," said Ray Lang, Amtrak.
Amtrak and Metra have filed a complaint in U.S. district court against British Developer Bill Davies who bought the post office two years ago with dreams of turning it into a shopping mall and offices.
Legal correspondence suggests that Davies' firm, International Property Developers, has not been paying ComEd for electricity to run the fans and that it wants Amtrak to take over the responsibility. The answer to that is no.
"But I'd rather solve the problem than win the lawsuit. Let's get it done. The sooner the better," said U.S. Senator Dick Durbin, who joined Amtrak and Metra officials Monday to add a bit of public pressure to their legal action.
"The diesel exhaust we're talking about contains 40 chemicals that have been proven to cause cancer," said Joel Africk, Respiratory Health Association.
In the last year, because of concern about the level of diesel exhaust in the train sheds, Metra has added new air filters to its cars, and among other things, has changed its fuel mix. But having fully working ventilation fans, Amtrak and Metra say, has long been legally required for the eight buildings that top the tracks.
In a statement Monday, International Property developers says "...we are sending three of our 11 extractor fans in for repairs this week. The other eight are fully functioning."
"Let me make this point again," said Durbin. "I don't want to win a lawsuit. I want to clean up the air in this building and if they're prepared to do this, we'll have a press conference and thank them".
A spokesperson for the owner of the old post office building says the ComEd bill has been paid in full and the three fans out for repair will be operational this month, which means the ventilation system will be working at full capacity.
There remains, however, a difference of opinion over who ultimately is responsible for operating and paying for the fans.