Train commuters in and around Chicago will soon be breathing cleaner air as all of the passenger cars on the Metra rail system are outfitted with more effective air purifiers.

The air filtration will be installed within 90 days and will achieve a Minimum Efficiency Reporting Value (MERV) of 13. That means the air filters are actually considered to be “medium efficiency” and will reduce diesel soot in Metra cars by 75 percent.

IQAir HyperHEPA filters, by the way, are rated MERV 16, the highest rating available.

Read more on the MERV rating system here:http://en.wikipedia.org/wiki/Minimum_Efficiency_Reporting_Value

Almost 250,000 riders pass through Chicago’s downtown commuter stations every day. They will still pass through much higher levels of diesels soot outside the Metra rail cars but will get a welcome relief while inside the cars.

Diesel soot levels in the first car behind the locomotive average 67 micrograms per cubic foot. That average dropped to 16 micrograms per cubic foot with the filters in place.

By contrast, outdoor air in the greater Chicago area averages 1 to 2 micrograms per cubic foot, according to the Chicago Tribune.

Elevated levels of diesel soot are associated with respiratory illness, cancer, heart attacks and premature death.Check out the level of diesel soot where you live, from the Clean Air Task Force, a nonprofit group, here:http://www.catf.us/diesel/dieselhealth/.

More than 37,000 passenger and freight rail cars move through the Chicago area each day, and the demand for rail transport in the area is expected to double in the next 20 years.