To ship UN 3528 engines legally, start by checking whether your equipment qualifies for the drained-fuel exemption under 49 CFR 173.220: if the fuel tank holds no more than 500 mL of residual fuel and is securely closed, a shipment moving by truck or rail is exempt from nearly every hazardous materials requirement. If you can’t meet that threshold, you’re in full compliance territory: shipping papers, Class 3 labels, trained employees, and, in most cases, PHMSA registration.
UN 3528 is the identification number for internal combustion engines, fuel cell engines, and machinery containing either, when the equipment holds or has held a flammable liquid fuel.1CAMEO Chemicals. UN/NA 3528 In practice that covers portable generators, industrial compressors, commercial lawnmowers, concrete saws, and similar equipment shipped with fuel in the system. The classification also covers engines running on combustible liquids (flash point above 60°C but below 93°C), which PHMSA has confirmed take the same UN number but with “Combustible liquid” replacing “3” in the hazard class column of the shipping paper.2Pipeline and Hazardous Materials Safety Administration. Interpretation Response 20-0044
Check the Exemption Before Anything Else
PHMSA has stated plainly that “because of the many exceptions provided to UN3528, internal combustion engines containing a flammable or combustible liquid are rarely subject to the HMR’s shipping paper requirements.”2Pipeline and Hazardous Materials Safety Administration. Interpretation Response 20-0044 Skipping this analysis and defaulting to full compliance is the most common mistake.
Under 49 CFR 173.220, an engine or piece of machinery qualifies for the exemption when the fuel tank has been drained and securely closed, with no more than 500 mL (about 17 ounces) of residual fuel remaining in the tank, engine components, or fuel lines.3eCFR. 49 CFR 173.220 – Internal Combustion Engines, Vehicles, Machinery Containing Internal Combustion Engines, Battery-Powered Equipment or Machinery, Fuel Cell-Powered Equipment or Machinery Self-propelled vehicles running on diesel get a bigger break: the tank does not have to be drained at all, provided space remains for fuel expansion and the cap is closed.
When an engine or machine meets these conditions and moves by motor vehicle or rail, it is not subject to any other requirements of the Hazardous Materials Regulations. No shipping papers. No hazmat labels. No placards. No emergency response phone number.
Air and vessel shipments are treated more strictly. Engines shipped by aircraft or vessel that are not installed in a vehicle must have all fuel, coolant, and hydraulic fluid drained as far as practicable, and any disconnected fluid pipes sealed with leak-proof caps.3eCFR. 49 CFR 173.220 – Internal Combustion Engines, Vehicles, Machinery Containing Internal Combustion Engines, Battery-Powered Equipment or Machinery, Fuel Cell-Powered Equipment or Machinery Some shipping paper and packaging requirements still apply even when the drained-condition standard is met.
When Full Compliance Applies
If the equipment holds more than 500 mL of fuel and doesn’t qualify for the diesel exception, the shipment is fully regulated. From that point forward, every downstream requirement in this article applies: shipping papers, markings, labels, placards above the weight threshold, trained personnel, and PHMSA registration.
Preparing the Shipping Paper
Under 49 CFR 172.202, the shipping paper must include the UN identification number, the proper shipping name, and the hazard class.4eCFR. 49 CFR 172.202 – Description of Hazardous Material on Shipping Papers A typical entry reads:
UN3528, Engine, internal combustion, flammable liquid powered, 3
For combustible-liquid fuels, “3” is replaced with “Combustible liquid.” The document, usually a Bill of Lading for surface transport or a Shipper’s Declaration for Dangerous Goods for air, must also list the quantity and any applicable technical details, including fuel type. IATA Packing Instruction 378 provides additional guidance for air freight, requiring precise entries for the quantity and type of dangerous goods on board.
Special Provision 363, referenced in the Hazardous Materials Table for UN 3528, adjusts documentation and disclosure based on the fuel tank capacity of the equipment. Larger fuel volumes trigger more detailed reporting so emergency responders know how much flammable liquid is in transit.
Markings, Labels, and Placards
Package Markings
Each non-bulk package must display the identification number preceded by “UN”—in this case, UN3528. Under 49 CFR 172.301, markings must be durable, printed in English, displayed against a sharply contrasting background, unobscured, and located away from advertising that could reduce their effectiveness. The UN number must be at least 12 mm high on standard packages, or 6 mm for packages of 30 liters or 30 kg or less.5eCFR. 49 CFR 172.301 – General Marking Requirements for Non-Bulk Packagings
When a non-bulk combination package holds inner packagings with liquid hazardous materials, orientation arrows must appear on two opposite vertical sides, pointing upright. Arrows must be black or red on a contrasting background.6eCFR. 49 CFR 172.312 – Liquid Hazardous Materials in Non-Bulk Packagings Certain exceptions apply, including inner packagings of one liter or less shipped by surface transport under limited quantity provisions.
Labels
A Class 3 flammable liquid label—the diamond marker with a flame symbol on a red background—must appear on each regulated package.1CAMEO Chemicals. UN/NA 3528
Vehicle Placards
UN 3528 is a Table 2 material for placarding. A transport vehicle must display Class 3 placards when carrying 454 kg (1,001 pounds) or more of aggregate gross weight of Table 2 materials.7Pipeline and Hazardous Materials Safety Administration. Placarding Requirements Below that weight, placarding is optional. When a vehicle carries non-bulk packages of two or more different Table 2 materials totaling less than 2,205 pounds loaded at one facility, a generic “DANGEROUS” placard can substitute.
Training Your Hazmat Employees
Every employee who handles, packages, labels, or prepares shipping papers for a regulated UN 3528 shipment counts as a hazmat employee and must be trained before performing those functions unsupervised. Under 49 CFR 172.704, training covers four areas:8eCFR. 49 CFR 172.704 – Training Requirements
- General awareness of the Hazardous Materials Regulations and how to recognize and identify hazardous materials.
- Function-specific training on the regulatory requirements tied to the employee’s actual duties.
- Safety training on emergency response, personal protective measures, and accident avoidance.
- Security awareness, including recognition of security risks in hazmat transport and how to respond to threats. New employees must complete this within 90 days of starting work.
Employees at companies required to maintain a security plan must also complete in-depth security training on the plan’s objectives, structure, and procedures. All hazmat training must be refreshed at least once every three years.8eCFR. 49 CFR 172.704 – Training Requirements
PHMSA Registration
Shippers and carriers of UN 3528 materials that require placarding must register with PHMSA under 49 CFR 107.601.9eCFR. 49 CFR 107.601 – Applicability If a shipment triggers placards under Part 172 Subpart F, the shipper needs a current registration. For the 2026–2027 registration year, the annual fee is $275 for small businesses and nonprofits, or $2,600 for other companies. Multi-year registration brings the per-year cost down slightly.
Shipments that fall within the 173.220 exemptions generally do not require placarding and do not trigger the registration requirement, which is one more reason to confirm exemption eligibility before assuming full compliance obligations apply.
Handing Off to the Carrier
Book transport with a carrier authorized to handle hazardous materials and submit the completed documentation package in advance. Carriers inspect the shipment at pickup to verify that exterior markings and labels match the shipping paper descriptions. Discrepancies between the physical package and the paperwork are the most common reason a carrier refuses a hazmat shipment at the dock, so a quick audit before pickup saves time.
Most carriers add a hazardous materials surcharge on top of standard freight rates. These fees vary by carrier and mode, so request a quote that itemizes the hazmat surcharge separately. After delivery, the carrier provides a signed proof of delivery referencing the hazardous material classification.
What Noncompliance Costs
Under 49 U.S.C. § 5123, a person who knowingly violates the hazardous materials transportation laws or any regulation issued under them faces a civil penalty of up to $75,000 per violation. If the violation results in death, serious illness, severe injury, or substantial destruction of property, the maximum climbs to $175,000 per violation.10Office of the Law Revision Counsel. 49 USC 5123 – Penalties Those base amounts are subject to periodic inflation adjustments.
Criminal penalties apply to willful or reckless violations: up to five years in prison and fines of up to $250,000 for individuals or $500,000 for corporations. When a violation causes the release of hazardous material resulting in death or bodily injury, the maximum prison sentence doubles to ten years. Even unintentional paperwork errors, such as a wrong UN number or a missing label, can trigger enforcement, which is why the exemption analysis under 173.220 is worth doing carefully before every shipment.