What Is the Symbol of Flammable Liquid? Meaning & Uses

The official symbol for a flammable liquid is a black flame set against a white background inside a red diamond border. Adopted by OSHA through the Globally Harmonized System (GHS), this pictogram warns that the contents can ignite at or below 199.4 °F (93 °C) and may release explosive vapors. It covers GHS Categories 1–3 and shows up on everything from lab vials to tank trucks.

Recognizing that small icon isn’t just a compliance box to tick—it’s a frontline defense against fires, fines, and injuries. Over the next few minutes you’ll see how the flame graphic differs on transport placards, NFPA diamonds, and workplace labels; the science behind flash points; where the mark is mandatory; and how to print durable, regulation-ready decals.

Need compliant labels fast? We’ll close with quick links to customizable flammable-liquid stickers and expert help from Safety Decals.

What Does the Flammable Liquid Symbol Look Like?

Whether you spot it on a tiny reagent bottle or a 53-foot tank trailer, the flame icon never strays far from its core design—a stylized blaze that instantly says “fire risk.” What changes is the surrounding shape, color field, and extra text demanded by different regulations. Below is a quick visual tour so you can tell each version apart at a glance.

Official GHS/OSHA Pictogram

The workplace label mandated by OSHA’s HazCom Standard features:

A black flame silhouette with three pointed tongues
Centered on a white background
Framed by a red diamond rotated 45° (square-on-point)

OSHA requires the pictogram to be at least 1 cm² and no smaller than 1/15 the total label area, ensuring it stays legible on everything from 30 mL vials to 55-gallon drums. The signal word (“Danger” or “Warning”) and hazard statements appear outside the diamond.

Variations in Transportation Placards (DOT, ADR, IMDG)

For highway, rail, sea, and air shipments, the U.S. DOT Class 3 placard swaps colors: a white flame and wording on a solid red background. Key elements include:

Element	Requirement
Background	Red, square-on-point (273 mm on each side)
Symbol	White flame
Text	“FLAMMABLE” (optional for bulk), hazard class number “3” at bottom
UN Number	Added for certain international loads (e.g., “UN1203” for gasoline)

ADR and IMDG placards look almost identical but may include language-free pictograms or subdivided panels for multilingual transport.

NFPA 704 Diamond and Color Codes

Inside facilities, firefighters look for the four-color NFPA diamond. The top (red) quadrant rates flammability on a 0–4 scale:

0 = will not burn
1 = flash point > 200 °F
2 = 100–200 °F
3 = 73–100 °F
4 = < 73 °F

Placed on building exteriors, lab doors, and tank farms, this system complements—but does not replace—GHS or DOT markings.

Common Misinterpretations to Avoid

Oxidizer: same flame but perched on a circle; yellow background in transport labels.
Pyrophoric/self-heating solids: share the GHS flame, yet classification text distinguishes them.
Explosive: bursting ball icon, orange background in transport.
Outdated EU orange square with “F” or “F+”: obsolete since 2015—use the red diamond instead.

Keeping these differences straight prevents costly mislabeling and helps emergency responders pick the right tactics if things go sideways.

Hazard Classes Behind the Symbol

Seeing the flame pictogram is only half the story; the other half is the science that decides when you must use it. Flammability isn’t arbitrary—it hinges on measurable properties such as flash point and boiling point that regulators worldwide have synchronized under the UN GHS.

Definition of Flammable Liquid and Flash Point Thresholds

A flammable liquid is any liquid with a flash point ≤ 93 °C / 199.4 °F as determined by closed-cup test methods like Pensky-Martens. The flash point is the lowest temperature at which a liquid emits enough vapor to ignite in air when exposed to an ignition source. The lower the flash point, the easier it is for the liquid to catch fire at room temperature.

GHS Categories 1, 2, 3 & 4 Explained

The GHS divides flammable liquids into four hazard categories that dictate label wording, precautionary statements, and shipping controls:

Category	Flash Point (°C)	Boiling Point (°C)	Signal Word	Required Pictogram
1	`< 23`	`≤ 35`	Danger	Flame
2	`< 23`	`> 35`	Danger	Flame
3	`≥ 23 and ≤ 60`	—	Warning	Flame
4*	`> 60 and ≤ 93`	—	Warning	Flame

*Category 4 is recognized in OSHA’s Safety Data Sheets but generally isn’t shown on shipped container labels in the United States.

Examples of Materials in Each Category

Category 1: diethyl ether, pentane—extremely volatile; vapors can ignite below freezing.
Category 2: gasoline, acetone—common solvents and fuels handled daily in labs and warehouses.
Category 3: diesel fuel, turpentine—ignite less readily but still demand strict controls.
Category 4: some glycol ethers, certain water-borne coatings—may seem “mild” yet still require the flame symbol on SDS and workplace labels.

Understanding where your product falls on this scale tells you not just which icon to print, but how aggressively to ventilate, ground, and segregate your storage.

Regulatory Standards Governing the Symbol

The little flame isn’t optional—it’s backed by a stack of regulations that span factory floors, shipping lanes, and emergency-response playbooks. Knowing which rulebook applies prevents you from ordering the wrong label stock or, worse, shipping a hazmat ticket magnet.

Global Harmonized System (GHS) Requirements

The UN “Purple Book” lays out harmonized label elements for every country that has signed on. For flammable liquids it mandates the red-bordered flame pictogram, a signal word (“Danger” for Categories 1–2, “Warning” for 3–4), standardized hazard statements, and numbered precautionary phrases. Nations may add local language but cannot alter the core graphics.

OSHA Hazard Communication Standard (HazCom 2012)

OSHA folded GHS into 29 CFR 1910.1200. Employers must label incoming containers, keep up-to-date Safety Data Sheets, and train workers. Since June 1 2016, shipped containers must carry the GHS pictogram in color; workplace “secondary” labels can use words or graphics as long as they convey equivalent information.

U.S. DOT Class 3 Placards and Labels

Transportation rules live in 49 CFR 172. Bulk packages over 119 gal need the red Class 3 placard with white flame and the number “3.” Non-bulk containers get a smaller but similar label. Limited-quantity and combustible-liquid exceptions ease requirements above 60 °C flash points.

NFPA 30 & NFPA 704 Fire Protection Codes

NFPA 30 prescribes storage quantities, venting, and grounding for flammables; NFPA 704 supplies the exterior diamond (red quadrant) that first responders use. These voluntary consensus standards complement, but never replace, OSHA or DOT mandates. Facilities typically display both systems side-by-side for full coverage.

Where the Flammable Liquid Symbol Must Be Used

Regulations don’t leave placement to chance. The flame pictogram has to follow the product everywhere it could pose a fire risk—from the first fill at the plant to long-term storage and every document in between. Missing or hidden icons are among the most common HazCom violations and a quick way to earn fines—or worse, fuel a preventable blaze.

Workplace Chemical Containers and Secondary Labels

Every shipped container already arrives with a GHS label, but once you pour solvent into a squeeze bottle, beaker, or wipe bucket, you must add an in-house label bearing the same flame symbol, product identifier, and hazard details. The only exemption is “immediate use” containers emptied by one person during the same shift.

Transportation and Shipping Containers

DOT Class 3 markings are compulsory on drums, IBC totes, cargo tanks, rail cars, and even small fiberboard boxes unless an official limited-quantity or combustible-liquid exception applies. Placards must be visible on each side and end of bulk vehicles and remain weather-fast for the trip’s duration.

Storage Areas, Cabinets, and Tanks

Yellow, self-closing flammable-liquid cabinets still need flame decals on the doors. Outdoor tank farms, piping manifolds, and room entrances require either OSHA-style pictograms or the NFPA 704 diamond so firefighters instantly know what’s inside before pulling hose.

Safety Data Sheets and Technical Documentation

Section 2 of every SDS must reproduce the pictogram in color. Electronic files, printouts, and laminated shop copies are all covered; grayscale or red-outline-only versions are non-compliant and can confuse readers in an emergency.

Designing and Sourcing Compliant Flammable Liquid Labels

A crisp, regulation-ready label does more than show the symbol of flammable liquid—it survives solvents, rain, and rough handling while staying easy to read. Before you hit “print,” square these four design pillars with OSHA, DOT, and your own workflow.

Size, Color, and Durability Specifications

Keep the GHS flame at least 1 cm² and not smaller than 1/15 of the total label area.
On small vials, a 20 mm × 20 mm diamond usually meets the rule; a 100 mm diamond fits 55-gal drums.
Red border should match roughly Pantone 485 C (±10 ΔE); white field must be high-contrast.
Aim for labels rated BS 5609 Section 2 if cargo might face saltwater immersion.

Material Choices for Indoor vs. Outdoor Use

Substrate	Best For	Pros	Watch-outs
Paper	Bench bottles	Cheap, easy to write on	Tears, smears with solvents
Vinyl	Warehouse drums	Flexible, UV-stable	Can shrink in high heat
Polyester	Tank farms, pipelines	Chemical & UV resistance, -40 °F to 300 °F	Higher cost

Digital Downloads vs. Professionally Printed Decals

Downloads (PDF, SVG): instant, editable, but be sure artwork is ≥300 dpi and colors are CMYK-accurate.
Pro decals: thermal-printed on UL-recognized film, include over-laminate, arrive ready to apply—ideal for high-traffic or outdoor assets.

Tips for Customizing Without Violating Standards

Never resize the flame inside the diamond—scale the whole icon proportionally.
Maintain clear space at least ½ × the pictogram width on all sides.
Place company logos or barcodes outside the red diamond; mixing graphics inside is non-compliant.
For mixtures requiring multiple pictograms, align them in a single field of view with a minimum 6 mm gap.

Best Practices for Employee Training and Risk Reduction

Labels alone don’t stop fires; people do. The tips below turn the flame pictogram into muscle memory and safe daily habits.

Teaching Workers to Recognize the Symbol

Kick off orientation with a slide of all GHS icons, then quiz crews during toolbox talks. Hand out wallet cards or QR-codes that jump to your SDS library.

Handling and Storage Guidelines

Ground and bond containers before pouring, keep ignition sources three feet away, and store below room temperature in ventilated, yellow NFPA-rated cabinets.

Emergency Response and Fire Suppression

Stage Class B extinguishers within 50 ft, practice spill-containment drills quarterly, and issue intrinsically safe flashlights for shutdowns during vapor releases.

Integration with Overall Hazard Communication Program

Document each training, update SOPs when formulas change, and align flammable-liquid procedures with your written HazCom and PSM plans to keep auditors—and firefighters—happy.

Related Hazard Symbols You Should Know

The flammable-liquid flame is only one of nine GHS pictograms. Spotting its look-alikes helps you store chemicals apart, choose the right extinguisher, and design labels that stay compliant when hazards stack up.

Flammable Gas vs. Flammable Liquid

Flammable gas uses the same flame but sits atop a gas cylinder outline in transport or shows a tiny bottle-shaped tank inside the red diamond under GHS. Storage rules shift: cylinders need pressure relief and upright chaining, while liquids demand grounding and spill containment.

Oxidizer, Explosive, and Corrosive Icons

Oxidizer: flame over a circle; yellow transport background—keep away from oils and greases.
Explosive: bursting ball; orange transport background—strict segregation, no sparks.
Corrosive: test tube eating metal and hand; black on white—requires acid-resistant PPE, separate from flammables.

Combining Multiple Pictograms on One Label

When a product is flammable and toxic, place both diamonds side by side with at least a 6 mm gap, ensuring all fit inside one field of view. Never shrink or overlap pictograms to save space.

Quick Answers to Common Questions (FAQ)

Got a thirty-second window? The cheat-sheet below resolves the four most-googled flammable-symbol questions in plain English.

How do I know if a chemical needs the flammable symbol?

Check the SDS: flash point ≤ 93 °C (199.4 °F) or listing as GHS Category 1–3 means the flame is required.

Can I use a black hazard diamond instead of red?

No. GHS insists on a red diamond; black borders show up only on DOT placards where the background is already red.

Is “highly flammable” different from “flammable”?

Under GHS, both terms land in Categories 1–2, share the identical flame, and rely on the signal word for severity.

Do water-based products ever need this symbol?

Surprisingly, yes—water-borne coatings, cleaners, or inks with enough volatile solvent can test below 93 °C, triggering the symbol despite their watery base.

Key Takeaways on Flammable Liquid Symbols

The red-bordered flame diamond means one thing: the liquid inside can ignite fast and burn hot. A flash point at or below 93 °C puts it in GHS Categories 1–3, triggering mandatory pictograms on containers, placards, storage areas, and SDSs. Use correct size, color, and materials, train staff, and you’ll satisfy OSHA, DOT, and NFPA—and avoid fires. Need compliant labels? Safety Decals can make them to spec.