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The handling and transport of hazardous materials, restricted matter, and perishable matter involves added levels of risk. That risk can become even greater if a nonmailable material is mailed or if the packaging of a mailable material is not adequate to prevent damage or spillage during normal handling.
Under no circumstances may any nonmailable hazardous material, restricted matter, or perishable matter be deposited for mailing. Mailable items must be packaged and labeled as required in the applicable DMM standards and the regulations in this publication.
A Postmaster may take any step reasonable and necessary to protect USPS employees and equipment from potentially dangerous or injurious materials or substances found in the mail. USPS employees may refuse an article for mailing if the content of the article is described by the mailer or otherwise revealed to be nonmailable.
The Postal Service’s primary purpose in requiring proper packaging, identification, and deposit of mailable hazardous materials, restricted matter, or perishable matter is to ensure the safety of our employees and the general public who may come into contact with these mailpieces. These requirements also are intended to ensure the safety of Postal Service equipment and facilities.