Oregon Public Broadcasting

If you saw thick black smoke at Portland International Airport Monday, there’s no need for concern. Fire and rescue workers simulated an airplane crash.

Airport spokesman, Steve Johnson, says they usually use propane, which burns without the smoke, but every now and then they need to use liquid fuel to mimic real-world conditions.

Steve Johnson: “We actually have a mock shell of an aircraft that we use for training purposes along with liquid fuel. It does produce some black smoke, but all the fuel is contained on the pad so it doesn’t seep into the ground.”

The FAA requires firefighters conduct a test every quarter.