A 2187 placard identifies the load as carbon dioxide, refrigerated liquid — a cryogenic Class 2.2 non-flammable, non-toxic gas under U.S. hazardous materials rules. The four digits in the center of the green diamond are the UN identification number, and they tell inspectors and emergency responders what is inside the tank before anyone reads a shipping paper. Everything else on the sign, and everything that must travel with it, is set by Title 49 of the Code of Federal Regulations.
What UN 2187 Actually Is
UN 2187 is carbon dioxide held as a liquid at roughly negative 109°F or colder.1National Oceanic and Atmospheric Administration. United Nations/North American Number Datasheet The Class 2.2 designation means it is neither flammable nor poisonous in the ordinary sense. That label understates the real risk. As the liquid warms, it expands rapidly into gas that is colorless and odorless, and in an enclosed trailer, dock, or basement it pushes breathable air out of the room. Asphyxiation can happen without warning.
The liquid itself is a frostbite hazard. Direct contact causes severe cryogenic burns, and the specialized insulated tanks used to move it are built to handle both extreme cold and the pressure that climbs as the liquid warms. Pressure relief valves vent gas before pressure reaches a dangerous level, which is why any release scene has to be treated as both an oxygen-displacement and a cold-injury problem.
What the Placard Has to Look Like and Where It Goes
The design specifications live in 49 CFR 172.519. The placard is a diamond (a square turned 45 degrees) with each side at least 250 mm, or about 9.84 inches. The background is green for Class 2.2 non-flammable gas, a gas cylinder symbol sits at the top, and the number 2187 is printed in black in the center. The material has to hold its color through a 72-hour fadeometer test and 30 days of open-weather exposure, which is why compliant placards are made of weather-resistant aluminum or vinyl rather than paper.2eCFR. 49 CFR 172.519 – General Specifications for Placards
Placement comes from 49 CFR 172.504: one placard on each side and each end of the transport vehicle, freight container, or rail car. In practice that means four signs — front, back, driver’s side, passenger’s side.3eCFR. 49 CFR 172.504 – General Placarding Requirements A faded, peeling, or missing placard is a violation on its own during a roadside inspection.
Shipping Papers That Must Travel With It
Every shipment of UN 2187 needs a shipping paper formatted under 49 CFR 172.202. The description reads, in order: identification number (UN2187), proper shipping name (Carbon dioxide, refrigerated liquid), hazard class (2.2), and total quantity. Class 2.2 gases do not get a packing group, so that field stays blank.4eCFR. 49 CFR 172.202 – Description of Hazardous Material on Shipping Papers
The paperwork must also carry an emergency response telephone number that is monitored the entire time the material is in transportation, including any storage along the way. Whoever picks up has to know the specifics of the shipment or reach someone who does. An answering machine or callback service does not count.5eCFR. 49 CFR 172.604 – Emergency Response Telephone Number
Along with the phone number, the driver must have emergency response information covering immediate health hazards, fire and explosion risks, spill-handling steps, firefighting methods, and preliminary first aid for this specific material.6eCFR. 49 CFR 172.602 – Emergency Response Information Many shippers satisfy this with the Emergency Response Guidebook or an attached safety data sheet. Before the truck rolls, the shipper certifies on the shipping paper that the carbon dioxide is properly classified, packaged, marked, and labeled.7eCFR. 49 CFR 172.204 – Shipper’s Certification The carrier keeps a copy of the paperwork for one year after accepting the shipment.
Who Can Drive It, and Where the Paper Sits
A driver hauling a placarded load of UN 2187 needs a commercial driver’s license with an “H” (hazardous materials) endorsement, or an “X” endorsement if the vehicle is also a tank. Either endorsement requires passing a written knowledge test and clearing a TSA security threat assessment that includes fingerprinting and a background check.8Transportation Security Administration. HAZMAT Endorsement
Once the driver has the paperwork, storage is regulated too. While driving, the shipping paper must be within immediate reach of the belted driver and either visible to someone entering the cab or held in a mount on the inside of the driver’s door. When the driver steps out, the paper goes into that door holder or onto the driver’s seat so a responder can find it fast.9eCFR. 49 CFR 177.817 – Shipping Papers Failing to produce the paper on request during an inspection can hold the vehicle until the documentation is corrected.
Training for Everyone Who Touches the Shipment
Anyone who handles, loads, or prepares paperwork for a UN 2187 shipment is a “hazmat employee” and has to be trained before working unsupervised. Federal rules break that training into four pieces:10eCFR. 49 CFR 172.704 – Training Requirements
- General awareness of hazmat regulations and how to recognize hazardous materials from labels, placards, and shipping papers.
- Function-specific training on the rules that apply to the actual job — filling out paperwork, loading tanks, driving.
- Safety training covering emergency response information, personal protective measures, and accident-avoidance procedures.
- Security awareness. New employees have 90 days from their start date to complete this piece.
Recurrent training is required at least once every three years. A lapse in the training cycle is its own violation and becomes an aggravating factor if something goes wrong on the road.
If Something Goes Wrong: ERG Guide 120
Responders arriving at a 2187 scene work from Guide 120 in the Emergency Response Guidebook, which covers inert gases including refrigerated liquids. The guide flags vapors that can cause dizziness or asphyxiation without warning and liquid that causes severe frostbite on contact.
The initial isolation distance is at least 100 meters (330 feet) in every direction from the release. Carbon dioxide gas is heavier than air, so it settles into ditches, basements, and storm drains and forms invisible asphyxiation zones. Responders stay upwind and uphill and wear self-contained breathing apparatus. If a tank is involved in fire, the isolation distance jumps to 800 meters — roughly half a mile — because heated containers can rupture. Cooling water is directed at exposed tanks but not at a leak or safety device, since icing can block a pressure relief valve and make the situation worse. A rising sound from a venting relief valve or discoloration of the tank means withdraw.1National Oceanic and Atmospheric Administration. United Nations/North American Number Datasheet
When You Have to Report an Incident
A telephone report to the National Response Center at 800-424-8802 is required as soon as practical when a hazmat incident in transportation produces any of the following:11eCFR. 49 CFR 171.15 – Immediate Notice of Certain Hazardous Materials Incidents
- A death or a hospitalization directly caused by the hazardous material.
- Evacuation of the general public for one hour or more.
- Closure of a major transportation route or facility for one hour or more.
- Any situation the person in charge judges to pose a continuing danger to life.
A written incident report on DOT Form 5800.1 is required for releases and for certain structural damage to cargo tanks with a capacity of 1,000 gallons or more, even where nothing has escaped. That written report is due within 30 days. Because a small cryogenic release in an enclosed space can trigger an evacuation quickly, the telephone threshold gets crossed with UN 2187 more often than the “non-toxic” classification would suggest.
What Violations Cost
Civil penalties under federal law reach up to $75,000 per knowing violation, rising to $175,000 per violation where the violation results in death, serious injury, or substantial destruction of property. Training-related violations carry a minimum penalty of $450.12Office of the Law Revision Counsel. 49 USC 5123 – Civil Penalty Those statutory figures are adjusted upward periodically for inflation, so the numbers actually enforced in any given year run somewhat higher than the floor in the statute.13Pipeline and Hazardous Materials Safety Administration. PHMSA Adjusts Maximum and Minimum Civil Penalties for Inflation
Violations stack. One shipment with a missing placard, an incomplete shipping paper, and an untrained employee behind the wheel is three separate violations, each with its own penalty exposure. Whether the conduct was willful, whether it created an actual safety risk, and the company’s compliance history all shape the final number. Criminal penalties are available for the worst cases, but most enforcement stays civil.