An explosives article or substance may not be transported to, from or within the United States without prior approval by the appropriate authority of the U.S. (see US 1), Attention: Approvals and Permits Division (PHH-30)). Consumer fireworks may be approved by the appropriate authority of the United States or certified by an approved fireworks certification agency. Such approval and certification remains valid for subsequent transport of the article or substance provided there is no change in its composition, design or packaging. Except as otherwise provided in 49 CFR 172.320, each package containing an explosives article or substance must be marked with the EX-number (or in the case of consumer fireworks an EX or FC number) assigned in the approval or certification for each substance, article or device contained in the package. The EX-number may also be provided in association with the description of dangerous goods on the transport document rather than marked on the package as provided in 49 CFR 172.320(d). Articles of the kind described in 49 CFR 173.56(h) and 49 CFR 173.166(c)(2) do not require prior approval or an EX-number.