By John Dodge

By John Dodge

CHICAGO (CBS) — A CTA commuter is being lauded as a hero this morning.

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The altruistic act?

Warning passengers that two of the seats on a Blue Line train were wet. It would be less altruistic if the person was the cause of the wetness, but we’ll give the commuter the benefit of the doubt.

A picture of two hand-written messages on lined notebook paper was posted on Reddit on Friday.

The exact cause of the wetness was not immediately known.

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However, veteran public transit riders say the No. 1 cause of damp seats is urine.

“Rule #39 of public transport: That liquid is always urine,” one commenter on Reddit said.

Others asked why CTA bothers with fabric seating, citing the New York subway, which has plastic seating.

Not only would it make the wet stains more noticeable, the seats would be easier to clean.

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“They should get rid of the cushioning,” one commenter said. “They could be cleaned quickly by a high-pressure spray.”