Specially designed filter cartridge classified as part of breathing apparatus, not as a general air filter.

A special filter cartridge designed exclusively for a self-rescuer breathing appliance was classifiable as a part of breathing apparatus under Heading 90.17/18, not as an air filter under Heading 84.18. The tariff analysis turned on the item's specific design and exclusive functional use with the breathing appliance, together with the Chapter 90 notes, which support classifying specially designed components with the appliance they serve. Because the record showed the cartridge was not suitable for general air-filter use and operated only in conjunction with the breathing apparatus, classification as a general air-filtering article was rejected.

---

---

Issues: Whether the imported filter cartridge for a self-rescuer breathing appliance was classifiable under Heading 84.18 as an air filter or under Heading 90.17/18 as a part of breathing apparatus.

Analysis: The imported item was a special filter cartridge meant for use only with the breathing appliance and was not an all-purpose air filter. Heading 84.18 covers air filters and other filtering machinery for liquids or gases, whereas Heading 90.17/18 covers breathing appliances, including gas masks and similar respirators. Applying the tariff headings and the Chapter 90 notes, the proper approach was to classify the component with the appliance for which it was specially designed. The record also showed that the component functioned only in conjunction with the breathing apparatus and was not suitable for general air-filter use.

Conclusion: The imported goods were correctly classifiable under Heading 90.17/18 as parts of breathing apparatus, not under Heading 84.18.

---