Smoke detector classification turns on detection function, not alarm output, so the goods fall under measuring instruments.

Imported smoke detectors using an ionisation chamber were classified according to their own detecting function, not as fire alarm apparatus. Technical literature, expert opinion and the device structure showed that the goods detected smoke concentration and did not themselves emit sound or visual alarm signals; they operated as complete instruments that triggered a connected alarm panel. The departmental reliance on the Explanatory Note was rejected because it concerned fire alarms incorporating smoke detectors, not the detector itself. The goods were therefore classified under Heading 9027.80 rather than Heading 8531.10, and the assessee's classification was upheld.

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Issues: Whether the imported smoke detectors were classifiable under Heading 8531.10 as fire alarms or under Heading 9027.80 as instruments and apparatus for measuring or checking quantities of heat.

Analysis: The imported goods were examined in the light of the technical literature, the DGTD opinion, the Chartered Engineer's certificate, and the structure of the detector. The material showed that the item functioned as an independent smoke detector using an ionisation chamber with a radioactive source, that it detected smoke particles and monitored smoke concentration, and that it did not itself emit sound or visual alarm signals. The Explanatory Note relied on by the department was found to concern fire alarms incorporating smoke detectors, not the detector itself. On this basis, the goods were held not to be fire alarms but complete instruments whose function was to detect smoke and trigger the connected alarm panel.

Conclusion: The smoke detectors were classifiable under Heading 9027.80 and not under Heading 8531.10, in favour of the assessee.

Final Conclusion: The impugned classification was set aside and the appeal succeeded with consequential relief.

Ratio Decidendi: A smoke detector that independently detects smoke through an ionisation chamber and does not itself produce an alarm signal is to be classified according to its detection function, not as a fire alarm apparatus.

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