A collapsed building and crushed cars block the entrance to a building. Hazardous materials linger inside. Firefighters search for survivors.

This is a mock disaster scenario. But what would happen if a chemical or biological incident happened in Chicago?

“We need to be ready, we need to be trained, we need to exercise our tools and we need to exercise our human beings that actually operate in that theater,” said Chief Timothy Walsh of the Chicago Fire Department.

Chicago first responders joined forces with the Illinois Fire Service Institute (IFSI) and the United States Marine Corps on Wednesday in a technical and hazardous material rescue training event at the city’s old post office annex.

The USMC Chemical Biological Incident Response Force (CBIRF) is a 500-person active duty unit. Its mission is to deploy to chemical, biological, radiological, nuclear or high-yield explosive threats or events in order to assist local, state or federal agencies.

“This is our first time in Chicago and we're looking to get out there and let the country know that we're here for them,” said CBIRF Captain Jordan Fox.

The search and rescue specialists can deploy with minimal warning.

“Hopefully, we never need the Marines to come here and bail us out, but we have to prepare every day like we are going to do that,” Walsh said.

According to the IFSI, the goal of the state-wide training effort is to improve the integration and interoperability of Illinois and federal disaster response capabilities.

“To be able to actually see it here today and all the moving parts come together, the intricacies, the planning, actually down to execution, I couldn’t be happier,” said Heather Moore of the Illinois Fire Service Institute.