In commerce, packages containing hazardous materials (except those qualifying as ORM–D material or a limited quantity shipment) must display the appropriate DOT diamond–shaped hazardous materials warning label. Any mailpiece bearing, or required under 49 CFR to bear, one of the warning labels shown in Exhibit 325a is prohibited from mailing. The warning labels shown in Exhibit 325b may appear only on mailpieces containing mailable hazardous materials that require use of the label under Postal Service requirements.
