Technician A says that SCR systems use DEF which results in toxic levels of ammonia being emitted from the tailpipe. Technician B says that Navistar engines certified for EPA MY 2013 and later use SCR systems. Who is correct??

Question

Quizplus · Accepted Answer

Technician B is correct because Navistar engines certified for EPA Model Year 2013 and later do indeed use Selective Catalytic Reduction (SCR) systems to meet emissions standards. SCR systems use Diesel Exhaust Fluid (DEF), which is primarily composed of urea and water, to reduce NOx emissions. When used correctly, SCR systems do not result in toxic levels of ammonia being emitted from the tailpipe, as the process is designed to convert NOx into nitrogen, water, and small amounts of CO2, which contradicts Technician A's statement.

Technician a Says That SCR Systems Use DEF Which Results