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General regulatory information for lab and clinic staff, not legal or medical advice. Confirm the current text of the rules before shipping.
Short answer
UN3291 is the identification number the U.S. Hazardous Materials Regulations assign to regulated medical waste. In 49 CFR 173.134, regulated medical waste is excluded from the Category B number UN3373 and “must be assigned identification number UN3291”. Waste that contains a Category A infectious substance is classed as an infectious substance instead.
Definition and scope
Under 49 CFR 173.134(a)(5), regulated medical waste (also called clinical waste or (bio)medical waste) means “a waste or reusable material derived from the medical treatment of an animal or human”, including diagnosis and immunization, or from biomedical research, including the production and testing of biological products. The same paragraph says such waste containing a Category A infectious substance must be classed as an infectious substance and assigned UN2814, UN2900 or UN3549.
How UN3291 is used in practice
The number matters when waste leaves the building. Section 173.197 sets the packaging rules for regulated medical waste, and the points below come from its text.
- Packagings must be rigid containers meeting subpart B of part 173.
- Non-bulk packagings must be UN standard packagings conforming to part 178 at the Packing Group II performance level, except as provided in 173.134(c).
- A non-bulk packaging used as a sharps container must be puncture-resistant for sharps and for sharps with residual fluid, shown by the part 178, subpart M performance tests, and must be securely closed to prevent leaks or punctures.
- A sharps container may be reused only if, among other conditions, it is specifically approved and certified by the U.S. Food and Drug Administration as a medical device for reuse and is permanently marked for reuse.
- For Large Packagings, carts and bulk outer packagings, inner packagings must be durably marked or tagged with the name and location (city and state) of the offeror, unless all contents come from one location and go to one location.
Section 173.134(c) adds exceptions for regulated medical waste moved by a private or contract carrier. The “INFECTIOUS SUBSTANCE” label is not required if the outer packaging carries a “BIOHAZARD” marking under 29 CFR 1910.1030. The specific 173.197 packaging rules are excepted for a rigid non-bulk packaging meeting 173.24, 173.24a and 29 CFR 1910.1030, provided the material does not include a waste concentrated stock culture of an infectious substance.
UN3291 compared with UN3373 and the Category A numbers
Most shipping-number confusion is a question of which definition the material meets. Each row below comes from 173.134.
| Material | Number | What 173.134 says |
|---|---|---|
| Regulated medical waste | UN3291 | The Category B definition “does not include regulated medical waste, which must be assigned identification number UN3291”. |
| Category B infectious substance (diagnostic or investigational specimen) | UN3373 | Described as “Biological substance, Category B”. |
| Regulated medical waste containing a Category A infectious substance | UN2814, UN2900 or UN3549 | Must be classed as an infectious substance, not as UN3291. |
The same material can move from one row to another depending on what it is. A patient sample in transit for diagnosis is a Category B question; once it is waste derived from treatment or research, it falls under the regulated medical waste definition.
Where it matters for labs and clinics
Section 173.134(c)(2) lists materials that may be offered as regulated medical waste when packaged in a rigid non-bulk packaging meeting 173.24, 173.24a and 29 CFR 1910.1030 and moved by a private or contract carrier in a vehicle used exclusively for regulated medical waste. Examples in the list include waste stock or culture of a Category B infectious substance, waste pharmaceutical materials, laboratory and recyclable wastes, rejected or recalled health care products, and sharps in qualifying sharps containers.
For the generator-side steps that come before transport, see regulated medical waste in a research lab, red bag waste, biohazard bag and container requirements, autoclave waste and regulated medical waste disposal and the wider lab waste disposal overview. For mail-back sharps programs see sharps container mail-back programs; for air shipments see IATA dangerous goods regulations.
Common misunderstandings
“Medical waste” and “Category B specimen” are the same thing
They are not. Section 173.134 keeps them apart: UN3373 is for Category B infectious substances and expressly excludes regulated medical waste.
Is there a “limited quantity” route for UN3291?
The sections to read are 173.134, which holds the exceptions for regulated medical waste, and 173.197, which holds the packaging rules. Whether a particular shipment qualifies for an exception depends on the carrier type, packaging and contents described in 173.134(c).
Is medical waste tracking part of the UN number?
No. The UN number identifies the material for transport classification. Tracking medical waste from generator to disposal is a separate matter; the research-lab guide covers the state-level side.
FAQ
What does UN3291 mean?
It is the identification number that 49 CFR 173.134 assigns to regulated medical waste, with 173.197 setting its packaging rules.
What is the difference between UN3291 and UN3373?
UN3373 describes Category B infectious substances such as diagnostic specimens; 173.134 states that this does not include regulated medical waste, which takes UN3291.
How is medical waste transport packaged?
In rigid containers; non-bulk packagings are UN standard packagings at the Packing Group II performance level, with puncture-resistant, securely closed sharps containers, subject to the exceptions in 173.134(c).
Who is named on the packaging?
Under 173.197(e), inner packagings for Large Packagings, carts and bulk outer packagings are marked or tagged with the offeror’s name and city and state, with one stated exception. Carriers are covered in medical courier services.
Sources
- 49 CFR 173.134, Class 6.2 (infectious substances) definitions and exceptions. law.cornell.edu/cfr/text/49/173.134. Checked 2026-10-30.
- 49 CFR 173.197, Regulated medical waste. law.cornell.edu/cfr/text/49/173.197. Checked 2026-10-30.
