The document describes an incident scenario at an oil refinery where a contractor crew unintentionally released hydrogen sulfide gas from a pipeline during maintenance work, which then ignited and caused a fire. As the refinery's emergency response coordinator, you must answer questions about the incident, including: (1) discussing hazards from interacting materials and byproducts, (2) actions the incident command should take to respond, (3) how the response would change if a nearby unit caught fire, and (4) corrective actions to prevent recurrence.