Story highlights Firefighters get a call that a chlorine canister put on a recycling plant's conveyor belt had burst

They arrive, without a hazmat team, to find that up to 30 people had been exposed to the gas

13 were transported to four area hospitals, and eight are in critical condition, a fire official says

(CNN) "It's a fire chief's worst nightmare."

That's how Spokane, Washington, Assistant Fire Chief Brian Schaeffer described crews arriving Wednesday knowing that dangerous levels of chlorine gas were in the air, people inside were in desperate need of help, and there was no hazardous materials team on their tail to make sure it was safe to go in.

But the firefighters went in anyway to find up to 30 people had been exposed to the toxic gas.

"When we got there, we had to focus on saving lives," Schaeffer said.

While most of the roughly 50 people then working at the plant were treated at the scene, eight were in critical condition at local hospitals on Wednesday night, Schaeffer said.

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