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Oct 11, 2023

NOx Sensor Probe Classified as Instrument for Chemical Analysis, Court Says

Subscribe to daily updates The Court of International Trade has ruled that a sensor probe that determines the concentration of nitric oxide in the exhaust gases of passenger vehicles and trucks is

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The Court of International Trade has ruled that a sensor probe that determines the concentration of nitric oxide in the exhaust gases of passenger vehicles and trucks is properly classified as an instrument for chemical analysis under HTSUS 9027.10.20, as contended by U.S. Customs and Border Protection, rather than as other electrical instruments and apparatus under HTSUS 9026.80.20.

This case involves an NOx sensor consisting of three elements: a probe, a wiring harness, and a sensor control unit. The most common application for this sensor is in a selective catalytic reduction system, which conditions a vehicle’s exhaust gas to remove pollutants before it is emitted. The sensor probe determines the concentration of NOx in exhaust gas by means of a cermet electrode. When the electrode comes in contact with NOx, an electrochemical reaction occurs which disassociates oxygen from nitrogen and generates an electrical signal that correlates to the concentration of NOx present in the exhaust. The electrical signal from the sensor probe is then sent to the SCU, translated, enhanced, and sent to the engine control unit. The ECU uses the information from the sensors, in conjunction with information from other components, to calculate the amount of ammonia that must be injected, in the form of a urea solution, into the selective catalyst reduction system. The ammonia reacts chemically with NOx molecules to create water and carbon dioxide, thus reducing the concentration of pollutant NOx in the exhaust gas.

The selective catalyst reduction system requires two NOx sensors to operate properly. One sensor is placed at the entrance of the system to determine the initial NOx concentration in the exhaust gas and a second sensor is placed at the exit to ensure that the NOx concentration has been reduced and that the selective catalyst reduction system is operating properly.

Among other things, the CIT found that the subject merchandise meets both categorical prongs of chemical analysis, thereby placing it within heading 9027. First, the sensor probe’s ability to separate and identify NOx molecules from within a mixed gaseous substance demonstrates its qualitative chemical analytical capabilities. The court noted in this regard that the determination of every individual component of a substance is not necessary to meet the common definition of an instrument or apparatus for chemical analysis; rather, the identification of one or more ingredients in a mixed chemical substance is sufficient. In addition, the sensor probe can quantify the amount of NOx in the exhaust gas, thereby producing an electrical signal proportionate to the concentration. Accordingly, it also meets the quantitative definition of chemical analysis because through an electrochemical process it generates information on the concentration or amount of NOx within the exhaust gas.

For more information on classification issues, please contact Deb Stern at (305) 894-1007.

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