John Zumkehr, president of Local 40-70 of the American Federation of Government Employees, says the officer was exposed Tuesday, rushed to a hospital, treated, and then later released.
He says it's a national problem at federal prisons, not just at Thomson.
"We've asked for simple equipment, drug detection equipment, ion machines, for our mailroom. That way when the stuff comes in they can test the mail for drugs and we can eliminate that."
But it also shows the prison needs to hire more people - currently there are 75 un-filled positions.
"Last month the union did six different job fairs - in a month. So as a union we're doing everything we can to help fix the problem and bring staff in, but it just takes time."
He says the prison officer exposed to drugs in the mailroom on Tuesday is now resting at home. A similar incident occurred three weeks ago, and after being hospitalized and then sent home, the officer is back at work.
Zumkehr hopes a new federal budget will include money for the Bureau of Prisons to buy mailroom screening equipment and advertise job openings at Thomson.