Technician A states that diesel exhaust oxidation catalysts function similarly to those used in automobiles. Technician B says that they must store noxious emissions when exhaust temperatures are low. Who is correct?

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Diesel exhaust oxidation catalysts (DEOC) are designed to reduce harmful emissions from diesel engines, but they operate according to different principles than those used in gasoline engines. Technician B accurately states that these catalysts must store noxious emissions at low exhaust temperatures, which is essential because diesel engines often have cooler exhaust temperatures that inhibit the effectiveness of the catalyst in oxidizing the emissions.

To function effectively across a range of operating conditions, many diesel exhaust systems employ a method known as "catalytic storage," where the catalyst temporarily holds back emissions until the exhaust temperature rises, at which point the stored emissions can be oxidized and converted into less harmful substances. This aspect is crucial for maintaining compliance with emission regulations and for the overall efficiency of the vehicle's emissions system.

Technician A's assertion that diesel exhaust oxidation catalysts function similarly to those in automobiles does not fully capture the different operational requirements and challenges that diesel engines present, particularly related to exhaust temperature and the types of emissions produced. Therefore, Technician B's description of the necessity for these catalysts to manage noxious emissions under low exhaust temperatures is the key point that confirms his correctness.

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