SPOKANE, Wash. -

Spokane firefighters entered Global Metal Technologies early Thursday with smoke in their face, like they've done so many times before, each wearing an oxygen mask because what they smelled from the outside was different.

They'd soon find out it was also potentially deadly.

A Spokane Police Officer called the Spokane Fire Department to the scene around 1 a.m. when he saw smoke coming from the roof of the building at 3200 E Trent Avenue. Once inside, a device firefighters use alerted them hydrogen cyanide was one of the chemicals in the smoke.

Assistant Fire Chief Brian Schaeffer said it's an agent used in manufacturing that can kill someone if enough is released.

"Hydrogen cyanide gas accumulated. It was actually, somehow through the ventilation system, let out," Schaeffer said.

Luckily, it wasn't dense enough to seriously affect people outside.

"Hydrogen cyanide is not something we really like to work with and it's definitely not something we want the public to be exposed to," Schaeffer said.

Trent Avenue was closed for more than an hour, so no drivers would inhale the fumes. Firefighters were decontaminated at the scene and their responding trucks were scrubbed. It was part of a plan firefighters execute when dealing with hazardous materials.

"There's a lot of (boxes to check) we have to go through primarily because people have been hurt in these type of incidents," said Schaeffer.

Crews develop strategies months in advance on how to fight fires at specific buildings in Spokane. Though crews didn't have a specialized plan for Global Metal Technologies, they're plan for the situation worked.

No one was injured but firefighters who responded will continue to have their health monitored.

"We could have had multiple patients, anywhere from five to hundreds. We've had incidents before with chlorine leaks and other similar chemicals where we had to do a larger expanded evacuation. Fortunately we didn't have to do that on this one," Schaeffer said.

The business was back open Thursday.

The fire department will continue to investigate the fire alongside the Department of Ecology.