Frequently Asked Questions

Urine and other specimens sent for drug or alcohol testing are typically exempt human specimens under USPS Publication 52, so they are not regulated as hazardous materials but must be triple packaged under section 346.327 before mailing (Publication 52, 346.12). USPS lists specimens for drug or alcohol testing as an example of samples with a low probability of being infectious.

Primary receptacle. A single primary receptacle must not hold more than 500 milliliters of a liquid specimen or 500 grams of a solid specimen. Several receptacles may share one secondary packaging if the combined amount stays within those limits. Each receptacle must be leakproof or sift proof and wrapped or separated with enough material to protect it and absorb the full contents if it leaks or breaks.

Secondary packaging. The receptacles, absorbent and cushioning must be sealed inside a leakproof (for liquids) or sift-proof (for solids) secondary packaging that can hold if a receptacle breaks in transit. The secondary packaging must be marked with the international biohazard symbol and fit snugly in a fiberboard box or container of equal strength.

Outer packaging. The outer packaging must be strong and rigid, and the secondary packaging cannot serve as the outer packaging. At least one side must measure at least 3.9 inches by 3.9 inches (100 mm by 100 mm). The address side must be marked "Exempt human specimen." Shipping documents and a content marking are not required.

When the exemption does not apply. A specimen that is a Category B infectious substance is not an exempt specimen and must be marked "Biological Substance, Category B" and UN3373 (Publication 52, 346.12). Category A infectious substances are nonmailable (Publication 52, 346.12 and 346.328).

Collection site practice. Packaging is one step in the custody process covered in the FAQ on drug testing chain of custody. Collector duties are described in the FAQ on what a specimen collector does, and receiving laboratories are covered in the FAQ on certified drug testing laboratories.

The FAQ on USPS mailer responsibility for hazardous materials explains who is accountable for a mailing, and the FAQ on USPS hazardous materials penalties covers enforcement.

Full responsibility rests with the mailer to comply with Postal Service and non-Postal Service laws and regulations when mailing hazardous material, and anyone who mails or causes to be mailed a nonmailable or improperly packaged hazardous material may face fines or imprisonment (USPS Publication 52, 323.1). The mailer must identify flashpoint, toxicity, corrosive or other hazardous properties before deciding whether an item is mailable.

Labels. Mailers must state whether a shipment contains hazardous materials when generating the label, including labels generated through USPS tools such as Click-N-Ship, USPS APIs or the Merchant Returns Application.

Service Type Codes. Mailers must use a unique hazardous materials Service Type Code (STC) in the Intelligent Mail package barcode or matrix barcode for each domestic outbound and return package containing hazardous materials, except packages bound for APO, FPO and DPO addresses, U.S. territories and possessions, and the Freely Associated States (Puerto Rico is not excepted). The STC must correspond to the product shipped. Combining several extra services, such as signature confirmation and insurance, is prohibited for hazardous materials mailings (Publication 52, 323.2).

Extra Service Codes. Packages containing hazardous materials must carry Extra Service Code 857. Domestic mailers may instead add one of 23 content-specific codes, and ESC 857 may then be omitted if the package record lacks enough extra service fields. USPS recommends the content-specific codes and may make them mandatory later (Publication 52, 323.3).

Shipping files and legacy postage. Mailers using PC Postage or USPS Ship platforms must transmit a Shipping Services File or Shipping Partner Event File with the applicable codes before or when tendering the shipment. Mailers using legacy postage meters or hard-copy postage statements must present hazardous materials shipments at a Postal Service retail or business mail entry unit (Publication 52, 323.4 and 323.5).

Transport outside the mail. Moving hazardous materials before they enter the mail and after they leave USPS custody is subject to DOT regulations (Publication 52, 323.1).

Training. DOT hazmat training for employees who handle shipments is covered in the FAQ on PHMSA hazmat employee training. Proposed changes to the DOT hazardous materials rules are covered in the news post on PHMSA's international harmonization proposal.

The FAQ on mailing drug test specimens covers exempt specimen packaging, and the FAQ on USPS hazardous materials penalties covers civil penalties.

A person who knowingly mails hazardous material in violation of 39 U.S.C. 3018 or a USPS regulation under it is liable for a civil penalty for each violation, plus clean-up costs and damages (39 U.S.C. 3018(c)(1)). As adjusted for inflation in the October 2026 eCFR text of 39 CFR 233.12, the penalty is at least $393 and up to $156,422 for each violation. The law also directs USPS to prescribe regulations for the safe transport of hazardous material in the mail.

What is prohibited. No person may mail or cause to be mailed hazardous material declared nonmailable by statute or USPS regulation, or mail it in violation of a rule on the time, place or manner of mailing. No person may manufacture, distribute or sell a container, packaging kit or similar device represented, marked, certified or sold for mailing hazardous material if it fails to meet the applicable standards (39 U.S.C. 3018(b)).

Knowing violations. A person acts knowingly with actual knowledge of the facts, or when a reasonable person exercising reasonable care would have had that knowledge (39 U.S.C. 3018(c)(2)).

Separate violations. Each day noncompliant hazardous material is in the mail is a separate violation, and each noncompliant item is a separate violation (39 U.S.C. 3018(c)(3)).

Hearings and penalty amounts. USPS may find a violation only after notice and the chance for a hearing. In setting a penalty, USPS must consider the nature and gravity of the violation, the violator's culpability, prior violations, ability to pay, effect on the business, the impact on USPS operations and other matters justice requires (39 U.S.C. 3018(d) and (e)).

Collection and court actions. USPS may compromise a penalty before suing to collect it. At USPS request, the Attorney General may bring a civil action seeking an injunction, civil penalties or punitive damages, in place of the administrative civil penalty for the same violation (39 U.S.C. 3018(f) and (g)).

Criminal exposure. USPS Publication 52 notes that improper mailings may also bring fines or imprisonment under title 18 of the U.S. Code (Publication 52, 323.1).

Related training. DOT hazmat training is described in the FAQ on PHMSA hazmat employee training.

The FAQ on USPS mailer responsibility for hazardous materials explains labeling and code duties.