Spark arresters work by trapping large carbon particles, which reduces the risk of fire. They are used in some internal combustion engines.
Spark arresters trap carbon particles greater than 0.023 inches in diameter and send them into the exhaust system. Centrifugal force throws the carbon against the walls of the arrester, where it is then sent through a filter. The most common types of filters used are screens and discs. These screens and discs must be manually cleaned periodically by the vehicle owner. Most installed spark arresters come with some type of cleanout plug to make accessing and cleaning the unit fast and easy.
Even small, handheld equipment with internal combustion engines, such as trimmers, brush cutters and blowers, have spark arresters. Engines with turbochargers sometimes have spark arresters, but properly maintained turbocharged engines do not need one because they function at such a high rate of speed, they ultimately rid themselves of large carbon particles.
Catalytic converters and mufflers are not considered spark arresters. They are made strictly to reduce noise and emissions, not to capture carbon particles that may start a fire. However, several brands of spark arresters have a catalytic function built in, to help with emissions.