Pressure-treated, fire-retardant, and chemically preserved wood products that don't fit more specific NAICS categories fall under this classification, covering a broad range of industrial and construction-grade lumber treated for durability or pest resistance. The treatment process — whether chromated copper arsenate, borate, or other preservatives — often determines end-use suitability and any applicable environmental or safety handling requirements. Importers should be aware that treated wood may be subject to EPA pesticide registration rules governing the preservative compounds used, adding a regulatory layer beyond standard customs clearance.

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