Hazmat Class Placards: Chart, Meanings, and When Required

Hazmat Class Placards: Chart, Meanings, and When Required

Hazmat Class Placards: Chart, Meanings, and When Required

Hazmat class placards are the diamond‑shaped signs you see on trucks, railcars, and containers that carry regulated hazardous materials. Each placard uses a mix of numbers, colors, words, and symbols to show the primary hazard class (and sometimes a division) so drivers, dock crews, and first responders can quickly recognize what’s inside. Under DOT rules, these placards are required in specific situations to communicate risk and keep people and property safe.

This guide gives you exactly what you came for: a clear, DOT‑aligned placard chart for Classes 1–9 and plain‑English explanations of what each one means. You’ll learn how to read placard parts, when placards are required (Table 1 vs. Table 2), special rules for bulk and Class 9, how mixed loads and the DANGEROUS placard work, placement and size requirements, common exceptions, and how to pick durable placards and holders. Let’s get you compliant, fast.

DOT placard chart: hazard classes 1–9 and what they mean

Use this quick chart to match hazmat class placards to their core hazards. Colors, numbers, and symbols are standardized so first responders can identify risks at a glance, and divisions clarify finer distinctions within several classes.

Class Typical color cue What it means Division notes
1 — Explosives Orange Explosive articles/substances; blast, projection, or fire hazards 1.1–1.6 range from mass explosion (1.1) to extremely insensitive articles (1.6)
2 — Gases Red/Green/White Flammable (red), non-flammable non-toxic (green), or toxic gases (white) 2.1 flammable; 2.2 non-flammable, non-toxic; 2.3 toxic
3 — Flammable liquids Red Liquids that ignite easily (e.g., gasoline, paints) —
4 — Flammable solids Red/white stripes; half white/half red; Blue 4.1 flammable solids; 4.2 spontaneously combustible; 4.3 dangerous when wet 4.1, 4.2, 4.3 identify the three hazard types
5 — Oxidizers/Organic peroxides Yellow; Red/Yellow 5.1 oxidizers intensify combustion; 5.2 organic peroxides may ignite/explode 5.1 oxidizer; 5.2 organic peroxide
6 — Toxic/Infectious White 6.1 toxic substances; 6.2 infectious substances (e.g., medical waste) 6.1 toxic; 6.2 infectious
7 — Radioactive Yellow/White Materials emitting ionizing radiation —
8 — Corrosive White/Black Substances causing severe skin/metal corrosion (e.g., sulfuric acid, NaOH) —
9 — Miscellaneous White with black vertical stripes (top) Miscellaneous hazards not elsewhere classified (e.g., dry ice, asbestos) —

Placard parts explained: numbers, colors, words, and symbols

Once you know what to look for, hazmat class placards read like a shorthand. Four cues do most of the work. The bottom number shows the hazard class (or division on some placards, like 1.1, 4.3, 5.2), standardized colors telegraph the family of hazard, optional words reinforce the message, and pictograms make the risk unmistakable. For explosives, a compatibility letter (A–S) may also appear.

  • Numbers: The numeral at the bottom identifies the hazard class; some placards display a division (e.g., 5.2).
  • Colors: Orange (explosives), red (flammable), green (non-flammable gas), yellow (oxidizer), white/black (corrosive), yellow/white (radioactive), and striped Class 9.
  • Words: Standard legends like “Flammable,” “Non-Flammable Gas,” “Corrosive,” or “Radioactive” clarify the hazard.
  • Symbols: Flame, exploding bomb, gas cylinder, skull and crossbones, corrosion-on-hand, and radiation trefoil quickly cue responders.

When placards are required by DOT (Table 1 vs. Table 2)

DOT placarding thresholds come from 49 CFR 172.504, which organizes hazards into two tables. In short, Table 1 materials must display hazmat class placards for any quantity, while Table 2 materials require placards when the aggregate gross weight of non‑bulk packages on a vehicle reaches 1,001 lb. Bulk packagings must be placarded regardless of weight. Carriers may also placard voluntarily if they follow Subpart F design and placement rules.

  • Table 1 — Placard any quantity: Includes the highest‑risk hazards (e.g., Div. 1.1–1.3 explosives, Div. 2.3 toxic gas, Div. 4.3 dangerous when wet, certain Div. 5.2 organic peroxides, “Poison Inhalation Hazard” materials in Div. 6.1, and certain Class 7 radioactive shipments). If it’s Table 1, placard it every time.

  • Table 2 — 1,001 lb threshold (non‑bulk): When a vehicle carries 1,001 lb or more total of Table 2 materials in non‑bulk packages, placard for each Table 2 hazard class present. Bulk packagings (tanks, IBCs meeting bulk definition) require placards at any weight. For mixed loads, the DANGEROUS placard may be an option (details below).

Bulk vs. non-bulk packaging and class 9 specifics

Placarding rules change with packaging size. Bulk packagings (e.g., cargo tanks, portable tanks, and IBCs that meet the bulk definition) must display hazmat class placards for the applicable hazard(s) regardless of total weight. Non‑bulk packages follow the Table 1 vs. Table 2 thresholds described above. Class 9 has a unique twist: placards are not required for non‑bulk Class 9 in domestic highway transport; however, a bulk packaging must be marked with the proper UN/NA identification number on either a CLASS 9 placard, an orange panel, or a white square‑on‑point display, per 49 CFR 172.504. Labels and other required markings still apply to individual packages.

Mixed loads and using the DANGEROUS placard

Mixed loads can create a placarding puzzle. DOT allows the DANGEROUS placard as a consolidation option when a transport vehicle or freight container carries two or more different Table 2 hazard classes in non‑bulk packages. It can replace multiple hazmat class placards and still meet 49 CFR 172.504, but only under specific conditions.

  • No Table 1 on board: If any Table 1 material is present, you must use that material’s specific placard(s)—never DANGEROUS alone.
  • Large quantity of one class: If a single Table 2 class comprises a significant portion of the load, display that class placard; DANGEROUS by itself isn’t sufficient.
  • Bulk still specific: Bulk packagings require the specific hazard placard, not DANGEROUS.
  • Optional alternative: You may always use all applicable class placards instead of DANGEROUS.

Subsidiary hazards and compatibility groups for explosives

Many hazardous materials present more than one risk. When a material has a subsidiary hazard, DOT requires placarding for the primary and the subsidiary class/division as applicable, with the hazard class or division number shown in the lower corner. This makes the combined risks obvious to responders. For explosives (Class 1), hazmat class placards may also display a compatibility group letter (A–S). That letter governs which explosive articles can ride together; mixing incompatible groups is restricted or prohibited.

  • Placard all applicable hazards: If a subsidiary hazard triggers placarding, display both placards and the correct division (e.g., 1.1–1.6).
  • Show compatibility letters on Class 1: Use the correct A–S letter to guide loading and segregation decisions.
  • No substitutions for Table 1: Explosives that are Table 1 must use their specific placards; do not replace them with DANGEROUS.
  • Voluntary placarding allowed: You may display additional placards when not required if they meet Subpart F design/placement rules.

Placement, visibility, and size rules for vehicles and containers

Correct placement is as critical as choosing the right hazmat class placards. DOT requires placards on each side and each end of a transport vehicle, freight container, or railcar, clearly visible from the direction they face (with allowances when units are coupled). Standard placards are approximately 10 x 10 inches and must be mounted square‑on‑point. Carriers often add extra placards on the tractor for added visibility, but required ones must meet Subpart F design and placement rules.

  • Four sides, unobstructed: Display at least four placards where the view isn’t blocked.
  • Upright and secure: Mount square‑on‑point, flat to the surface or in a holder; no folding or curling.
  • Clean and legible: Keep free of dirt, snow, or damage; replace faded or torn placards promptly.
  • Not hidden by equipment: Don’t let ladders, hoses, doors, or tarps cover placards.
  • Correct legend/number: Show the proper class/division number in the lower corner as required.

Placards, labels, and markings: what’s the difference?

Think of these as three complementary signals. Hazmat class placards communicate hazards for the transport unit itself; labels communicate hazards on each individual package; markings provide the specific identity of the material. Used together, they tell responders both “what kind of danger” and “exactly which substance” is present.

  • Placards (vehicle/container): Diamond signs, typically about 10 x 10 inches, mounted square‑on‑point on each side and end. They show the hazard class/division number and standardized colors/symbols; required under 49 CFR 172.504 based on Table 1 vs. Table 2 and bulk rules.
  • Labels (packages): Smaller diamond labels applied to individual non‑bulk packages. They mirror placard colors/symbols to indicate the package’s primary (and subsidiary) hazard, even when the vehicle itself may not need placards.
  • Markings (identity info): Alphanumeric information such as the four‑digit UN/NA identification number and proper shipping name on packages and bulk packagings. For bulk, the ID number may appear on a Class‑specific placard, an orange panel, or a white square‑on‑point (e.g., Class 9 per 49 CFR 172.504).

Exceptions and special cases (limited quantities, materials of trade, combustible liquids)

Not every shipment that contains hazardous materials needs hazmat class placards. DOT provides targeted exceptions that reduce placarding without compromising hazard communication. Use them only when you meet all packaging, quantity, and marking conditions—and remember you may voluntarily placard if your signs meet Subpart F design/placement rules.

  • Limited quantities (LQ): When packaged and marked as limited quantity, most Table 2 materials moved by highway are generally excepted from placarding. The LQ mark and required package labels/markings still apply; bulk packagings are not LQ.

  • Materials of trade (MOT): Small amounts carried by a business to support its operations (e.g., service vehicles) can move under MOT limits without placards when packaged, marked, and secured per the rule. Quantity caps and basic hazard info are required.

  • Combustible liquids (domestic): Non‑bulk combustible liquids are typically excepted from placarding in highway transport. Bulk packagings must be properly marked with the UN/NA ID number and, depending on the proper shipping name, may require a class‑specific placard; consult 49 CFR 172.504 for applicability.

How to read UN/NA identification numbers quickly

The four-digit UN/NA identification number is the fastest way to pinpoint what’s in a vehicle. On highway shipments, it’s typically centered on the placard; for bulk, you may see it on an orange panel or a white square‑on‑point (e.g., for Class 9 per 49 CFR 172.504). Combine that number with the placard’s color, symbol, and bottom class/division to verify the hazard.

  • Spot the code: Look for UN or NA plus four digits (UN 0004–3534; NA 8000–9279).
  • Confirm placement: Center of placard, orange panel, or white square‑on‑point (bulk).
  • Read the class/division: Check the numeral at the bottom (e.g., 2.1, 5.2).
  • Cross‑check papers/ERG: Match the ID to the proper shipping name and guide.
  • Scan for subsidiary placards: Additional risks may be present.
  • If obscured or missing: Do not move the unit until corrected.

Choosing materials and mounting options for placards

The right construction and mounting keep hazmat class placards readable after rain, road spray, wash bays, UV, and fuel exposure. Choose durable faces and secure holders so signs stay square‑on‑point, legible, and unobstructed on each side and each end of the vehicle or container.

  • Rigid holders (aluminum/stainless): Corrosion‑resistant slide‑in frames that keep placards flat and secure.
  • Flip‑placard systems: Fast, tool‑free switching between approved legends; locking tabs prevent mis‑display.
  • Magnetic placards: Good for steel trailers and rentals; verify pull strength for highway speeds.
  • Adhesive/weatherable vinyl: Short‑term use; replace if faded, torn, or contaminated by fuel/solvents.
  • Reflective faces (where permitted): Boost night visibility; ensure colors/symbols meet Subpart F specs.
  • UN/NA panels: Use frames that accept orange panels or white square‑on‑point inserts for bulk ID numbers.

Quick compliance checklist for shippers and drivers

Use this pre-shipment/pre-trip checklist to turn the rules above into action. It distills 49 CFR 172 Subpart F and 172.504 so you can verify classification, thresholds, and placement before rolling. If unsure, you may placard voluntarily as long as design and placement meet Subpart F.

  • Identify the material: Confirm proper shipping name and UN/NA four‑digit ID.
  • Classify hazards: Verify primary class/division and any subsidiary hazard.
  • Size matters: Determine bulk vs. non‑bulk packaging.
  • Table 1 rule: Placard any quantity of Table 1 materials.
  • Table 2 rule: Placard ≥1,001 lb aggregate of non‑bulk; bulk placard regardless.
  • Mixed loads: DANGEROUS placard only for multiple Table 2 non‑bulk classes; never with Table 1 or for bulk; use specific placards if one class predominates.
  • Explosives (Class 1): Show correct division (1.1–1.6) and compatibility letter A–S when required.
  • Class 9 bulk: Display ID number on a Class 9 placard, orange panel, or white square‑on‑point.
  • Placement/legibility: Each side and each end, square‑on‑point, unobstructed; correct class/division number in the lower corner; clean, secure, and unfaded.
  • Paperwork check: Shipping papers match placards and IDs; driver carries emergency response info and reinspects at stops.

Where to buy DOT‑compliant hazmat placards

Buy from a supplier that certifies placards meet 49 CFR Subpart F specs (size, colors, symbols, durability) and provides holders or panels for UN/NA numbers. Safety Decals manufactures DOT‑compliant hazmat class placards and mounting systems with customizable legends, division numbers, and compatibility letters—available in rigid flip or slide‑in frames, magnetic, or weatherable vinyl faces sized for 10 x 10, square‑on‑point visibility on each side and end.

Key takeaways

You don’t have to memorize the whole regulation—just the essentials that keep you compliant and safe. Use the placard’s color, symbol, and bottom number to identify the hazard; use the UN/NA ID to pinpoint the substance; and apply 49 CFR 172.504 thresholds to know when to placard.

  • Table 1 = placard any quantity; Table 2 = placard at ≥1,001 lb (non‑bulk).
  • Bulk packagings = placard regardless of weight.
  • Class 9 bulk: show the UN/NA ID on a Class 9 placard, orange panel, or white square‑on‑point.
  • DANGEROUS placard: only for multiple Table 2 non‑bulk classes; not for Table 1 or bulk.
  • Explosives: display correct division (1.1–1.6) and compatibility letter A–S when required.
  • Placement: each side and each end, square‑on‑point, clean, and unobstructed.
  • Exceptions exist (LQ, MOT, certain domestic combustibles)—use only when fully qualified.

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