Hundreds of National Guard troops and local first responders are training for the unthinkable.

The troops and emergency workers took part in a simulated chemical weapons attack Thursday.

Volunteers represented casualties in a mock-up of a small town.

Troops worked to collect the wounded and get them through a decontamination line.

The soldiers say the hands-on training is practically like a real emergency.

"Every time we run a scenario we find things, we readjust and we keep going," S.Sgt. Charissa Taylor with the 128th Chemical Company from Philadelphia said. "We basically are always improving."

National Guard leaders say the training is vital because a chemical attack could happen anywhere, not just in a combat zone.

The Guard is gearing up to help with security in Pittsburgh for next month's G-20 summit.