What device removes particles from the air before it enters the engine?

An air filter removes particles from incoming air before that air enters an engine.

The filter protects the engine’s cylinders from abrasive dust, dirt, and other particles that could accelerate wear and contaminate the lubricating oil. It sits in the intake system, usually inside an air-cleaner housing upstream of the throttle body or carburetor. Clean, appropriately sized filtration is important because the engine must receive both air and fuel in the correct proportion.

Most fuel-injected cars use a pleated paper filter shaped as a flat panel. Older carbureted vehicles commonly used a cylindrical filter mounted above or beside the carburetor. Foam, cotton gauze, stainless-steel mesh, and oil-bath designs also exist, especially in specialized or older applications.

The catalytic converter belongs in the exhaust system and treats pollutants after combustion. A fuel filter cleans gasoline or diesel, while an oil filter cleans engine lubricant; none of those filters performs the intake-air job. A clogged air filter can restrict airflow, although a properly sized paper filter usually creates little restriction until it becomes heavily dirty. Cabin air filters protect occupants, not the engine.