F MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F01 MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
F01N GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
2550/00 Monitoring or diagnosing the deterioration of exhaust systems
F01N2550/14 Systems for adding secondary air into exhaust