Hazmat Placard Requirements in the US

A US hazmat placard tells you the hazard class or division of what's in the vehicle or container. You read it from the class or division number in the bottom corner, the background colour and, usually, a word such as FLAMMABLE or POISON. 49 CFR 172.519 says the number "must be displayed in the lower corner". It also says hazard text "is not required" on any placard except the Class 7 (RADIOACTIVE) and DANGEROUS placards. On the OXYGEN placard the text can be left off only if the identification number is shown instead.

Approach: The only US DOT text in the datasets is the § 172.101 Hazardous Materials Table, so I read the current eCFR text of 49 CFR 172.519 to 172.560 (placard specifications) and 49 CFR 173.2 (hazard class index). The regulation shows each symbol only as a drawing, so I haven't described the symbols in words.

What each placard means and how to recognise it

The meaning is the class or division name from 49 CFR 173.2. The design is from the placard's own section.

Placard (section)	Class / division and meaning (§ 173.2)	Colours required
EXPLOSIVES 1.1, 1.2, 1.3 (§ 172.522)	1.1: mass explosion hazard; 1.2: projection hazard; 1.3: mainly a fire hazard	Orange background; black symbol, text, numerals and border. The "*" is replaced by the division number and, when required, the compatibility group letter
EXPLOSIVES 1.4 (§ 172.523)	1.4: no significant blast hazard	Orange; black text; "1.4" at least 64 mm high
EXPLOSIVES 1.5 (§ 172.524)	1.5: very insensitive explosives; blasting agents	Orange; black text; "1.5" at least 64 mm high
EXPLOSIVES 1.6 (§ 172.525)	1.6: extremely insensitive detonating substances	Orange; black text; "1.6" at least 64 mm high
FLAMMABLE GAS (§ 172.532)	2.1: flammable gas	Red; white symbol, text and number
NON-FLAMMABLE GAS (§ 172.528)	2.2: non-flammable compressed gas	Green; white symbol, text and number
OXYGEN (§ 172.530)	Oxygen; used in place of NON-FLAMMABLE GAS (see note 1)	Yellow; black symbol, text and number
POISON GAS (§ 172.540)	2.3: poisonous gas	White, with a black upper diamond; black text and number
FLAMMABLE (§ 172.542)	3: flammable liquid	Red; white symbol, text and number. "GASOLINE" may replace "FLAMMABLE" on cargo or portable tanks carrying gasoline by highway
COMBUSTIBLE (§ 172.544)	3: combustible liquid	Red; white symbol, text and number. "FUEL OIL" may replace "COMBUSTIBLE" on cargo or portable tanks carrying fuel oil (not classed flammable) by highway
FLAMMABLE SOLID (§ 172.546)	4.1: flammable solid	White with seven vertical red stripes; black symbol, text and number
SPONTANEOUSLY COMBUSTIBLE (§ 172.547)	4.2: spontaneously combustible material	White upper half, red lower half; black symbol, text and number
DANGEROUS WHEN WET (§ 172.548)	4.3: dangerous when wet material	Blue; white symbol, text and number
OXIDIZER (§ 172.550)	5.1: oxidizer	Yellow; black symbol, text and division number
ORGANIC PEROXIDE (§ 172.552)	5.2: organic peroxide	Red top half, yellow lower half; black text and number; the symbol may be black or white
POISON (§ 172.554)	6.1: poisonous materials	White; black symbol, text and number. "TOXIC" may be used instead of "POISON"
POISON INHALATION HAZARD (§ 172.555)	6.1 poisonous by inhalation (see note 2)	White, with a black upper diamond; black text and number
RADIOACTIVE (§ 172.556)	7: radioactive material	Yellow triangle in the upper part, white below; black trefoil symbol, text and number
CORROSIVE (§ 172.558)	8: corrosive material	White triangle in the upper part, black below; white text and number; black symbol
CLASS 9 (§ 172.560)	9: miscellaneous hazardous material	White, with seven black vertical stripes on the top half; the class number 9 underlined and centred at the bottom
DANGEROUS (§ 172.521)	Mixed load of two or more Table 2 categories in non-bulk packages (§ 172.504(b), see the earlier answer)	Red upper and lower triangles; white centre and border; black inscription

Notes to the table:

1. Under § 172.504(f), covered in the earlier answer, OXYGEN may replace NON-FLAMMABLE GAS for domestic oxygen, compressed or refrigerated liquid.
2. Under § 172.505, also covered earlier, this placard is required on top of the primary placard.
3. Division 6.2 (infectious substance) is listed in § 173.2, but it has no placard because placarding does not apply to infectious substances (§ 172.500).

Design rules common to all placards (§ 172.519)

• Shape and size: a diamond (square on point) at least 250 mm (9.84 in) per side. It must have a solid inner border about 12.5 mm inside the edge.
• Lettering: class or division numbers, and any hazard text, at least 41 mm (1.6 in) high unless a placard's own section says otherwise.
• Colour: colours must fall within the DOT Hazardous Materials Label and Placard Color Tolerance Chart. The PANTONE formula guide may be used as an alternative.
• Durability: colours must survive a 72-hour fadeometer test and 30 days of open weather.
• International shipments: for shipments under 49 CFR Part 171 Subpart C, placards meeting the UN Recommendations, ICAO Technical Instructions, IMDG Code or Transport Canada TDG Regulations "may" be used. Loads containing a material poisonous by inhalation are the exception: they must be placarded to the DOT specifications.
• Rail and highway route controlled quantity loads: some rail-car placards (§ 172.510(a)), and placards on motor vehicles carrying highway route controlled quantity radioactive material (§ 172.507), sit on a square background. The background is a white square of 14¼ in (362 mm) with a black border out to 15¼ in (387 mm) (§ 172.527).

Each class has a full legal definition in the Part 173 section listed in § 173.2, for example § 173.120 for Class 3 and § 173.136 for Class 8. I can pull any of them if you need the classification criteria.

Sources:

• 49 CFR Part 172 Subpart F (§§ 172.519 to 172.560)
• 49 CFR 173.2

Labels go on individual packages. Placards go on the bulk packaging, freight container, vehicle or rail car that carries them. Under 49 CFR 172.400(a), each non-bulk package and each smaller bulk unit "must" be labelled. Larger units are placarded under Part 172 Subpart F (§ 172.504). The two systems use the same hazard classes and the same diamond design, but they differ in size, where they go, what triggers them and how subsidiary hazards are shown.

Approach: The only US DOT text in the datasets is the § 172.101 Hazardous Materials Table, so I read the current eCFR labelling sections (§§ 172.400, 172.400a, 172.402, 172.406, 172.407). I compared them with the placarding sections covered in the earlier answers.

Side-by-side

	Labels (Part 172 Subpart E)	Placards (Part 172 Subpart F)
Goes on	Non-bulk packages, plus some smaller units (see note 1) (§ 172.400(a))	Each side and each end of bulk packagings, freight containers, unit load devices, transport vehicles and rail cars (§ 172.504(a))
Minimum size	Diamond at least 100 mm (3.9 in) per side, with a 5 mm inner border. The size may be reduced proportionally if the symbol and other elements stay clearly visible (§ 172.407)	Diamond at least 250 mm (9.84 in) per side, with a border about 12.5 mm inside the edge (§ 172.519)
Class number	"Must be displayed in the lower corner" of primary and subsidiary labels, 6.3 to 12.7 mm high (§§ 172.402(b), 172.407)	In the lower corner, at least 41 mm high unless the placard's own section says otherwise (§ 172.519)
Weight threshold	No aggregate-weight threshold in § 172.400: each package bears its labels	Table 2 materials by highway or rail need no placard below 454 kg (1,001 lb) aggregate gross weight, except in bulk packagings (§ 172.504(c))
Subsidiary hazards	Primary and subsidiary labels as listed in column 6 of the § 172.101 Table (§ 172.402(a)). They must be displayed within 150 mm (6 in) of one another (§ 172.406)	Mostly the primary hazard only. Subsidiary placards are required only for poison inhalation hazard, dangerous when wet and uranium hexafluoride (§ 172.505)
Mixed loads	Each package carries its own labels	The DANGEROUS placard may be used for mixed Table 2 loads (§ 172.504(b))
Durability	Must survive a 30-day exposure to conditions of transport and a 72-hour fadeometer test (§ 172.407)	Must survive a 72-hour fadeometer test and 30 days of open weather (§ 172.519)

Notes to the table:

1. The smaller units are: bulk packaging under 18 m³ (640 ft³); portable tanks under 3,785 L; DOT 106/110 multi-unit tank cars; and overpacks or freight containers under 18 m³. Each needs labels only if it is not placarded.
2. Placards are covered by §§ 172.504 to 172.505.

Where the two systems overlap

• Small bulk units: labels are an alternative to placards. § 172.400(a) requires labels on these units unless they are placarded. § 172.514 lets the same kinds of units be labelled instead of placarded.
• Placarded containers: § 172.400a exempts freight containers and unit load devices that are placarded from labelling.
• Overpacks: labels need not be repeated on an overpack or unit load device when the package labels remain visible (§ 172.400a).

Things only labels have

• Division 6.2 INFECTIOUS SUBSTANCE label (§ 172.432): there is no infectious-substance placard, because placarding does not apply to infectious substances (§ 172.500).
• Class 7 label variants and FISSILE and EMPTY labels (§§ 172.436 to 172.450): the Radioactive Yellow III label is what triggers the RADIOACTIVE placard under Table 1.
• CARGO AIRCRAFT ONLY label: a person offering or transporting by air hazmat that is authorised on cargo aircraft only "shall label the package" with it (§ 172.402(c)). It must be at least 110 × 120 mm (§ 172.407).
• Placement rules for packages (§ 172.406):
  • not on the bottom surface;
  • for air transport, the entire label must appear on one side of the package;
  • duplicate labels on two sides for packages of 1.8 m³ or more and for non-bulk radioactive packages;
  • a label "may not be obscured by markings or attachments".

Exceptions that differ

Labelling exceptions (§ 172.400a):

• certain Dewar flasks and cylinders;
• cylinders permanently mounted on vehicles;
• some military shipments;
• toy caps;
• some subsidiary labels: no 6.1 label on Class 8 materials whose toxicity comes only from corrosive action, and no 4.1 label on Division 4.2 packages.

Placarding exceptions (§ 172.500): placarding does not apply to limited quantities, small quantities, infectious substances or combustible liquids in non-bulk packagings.

To find which labels a specific material needs, look up its § 172.101 Table entry (column 6 gives the label codes). I can pull that for any proper shipping name or UN number.

Sources:

• 49 CFR 172.400
• 49 CFR 172.400a
• 49 CFR 172.402
• 49 CFR 172.406
• 49 CFR 172.407