Flames erupt during a natural gas pipeline explosion in Greensburg, Pa. in 2016. The explosion, which burned one person, caused flames to shoot above nearby treetops in the largely rural Salem Township, about 30 miles east of Pittsburgh, and prompted authorities to evacuate businesses nearby.

Mariner East 2: What are natural gas liquids, and what happens if they leak?

The pipeline will carry volatile propane, ethane and butane, which has raised fears of many who live near it — even though explosions are rare. As part of StateImpact Pennsylvania’s “Mariner East 2: At what risk?” series, we put together this video to explain what those substances are and how they act both inside the pipeline and if they got out, and how you should respond if there’s a leak.

By Susan Phillips and Tom Downing