(under subclass 34) Subject matter wherein the engine* is an internal combustion engine and regulation of the engine* includes means to regulate the discharge of undesirable engine waste gas constituents.
SEE OR SEARCH CLASS
60, Power Plants,
272+, for an internal combustion engine with treatment or handling of exhaust gas.
123, Internal-Combustion Engines, appropriate subclasses for engine emission control in the absence of a gear transmission.
