Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: Some of the pollutants from fossil fuels can be filtered out of exhaust before it is released into the air. Other pollutants can be changed to harmless compounds before they are released. Two widely used technologies are scrubbers and catalytic converters. Answer: fossil fuels
A:
A catalytic converter filters pollutants in exhaust created by burning what before releasing it into the air?