The best caution symbols are the ones people recognize in under a second, that display correctly when you paste them, and that match a real hazard category. For a general alert, copy ⚠. For toxic or infectious material, use ☠ or ☣. Use ☢ for radiation, ⚡ for electrical shock, and 🚧 for work zones. Writers, app builders, and safety managers will use the first pick most. Lab staff will lean on the second through fourth. Electricians and facility teams need the fifth, and site supervisors need the sixth.
Search results for this topic bury you in thousands of icon files, emoji tables, and clip art. Almost none of them tells you what a symbol is allowed to mean on a real sign. That gap causes mistakes, such as a yellow triangle where a red danger sign is required, or a decorative skull on a label that carries legal weight.
This article lists six symbols. Each one gets its meaning, a character you can copy and paste, and a note on where it belongs. Safety Decals is a family-owned Michigan company that traces its roots to 1947 and makes safety decals for businesses, so the usage notes come from the sign side as well as the screen side. The characters below are plain text, so they use the fonts on your device and need no download.
1. Warning sign: the general caution triangle
The warning sign is the standard answer to "what is a symbol for caution?" It is a triangle with an exclamation mark, and it tells the viewer that a hazard is present without naming it.
What it means
Unicode calls this character WARNING SIGN (U+26A0). You will also see it called the exclamation triangle or caution sign. On physical signs, ISO 7010 lists the same graphic as W001, the general warning symbol. It is the right pick when you want attention but have no specific pictogram for the hazard.
The triangle never says how serious the risk is. That job belongs to the signal word beside it. Under ANSI Z535, CAUTION on yellow covers hazards that can cause minor or moderate injury, WARNING on orange covers serious injury or death, and DANGER on red covers imminent, severe hazards.
A triangle tells people to look, and the signal word tells them how worried to be.
Copy and paste
Select the character below and paste it into any field that accepts text. It renders as a flat black glyph in some fonts and as a colored emoji in others, so test it on the device your readers use before you rely on it.
⚠
⚠
If you need an image instead of a character, choose SVG when the icon must scale cleanly for web or print, and PNG for slides and documents. Read the license on any free icon before commercial use, and check whether it requires attribution.
Where to use it
Use ⚠ in emails, dashboards, spreadsheets, software alerts, and training slides. Do not treat it as a compliant label for a machine or a floor. A physical sign needs a signal word, correct colors, and readable text.
The Safety Decals Caution decal measures 7" W x 5" H and costs $4.99 to $14.99. For another size or design, email sales@safetydecals.com.
2. Skull and crossbones for toxic hazards
The skull and crossbones means a substance can kill or seriously harm you if you swallow it, breathe it, or absorb it through your skin. It is the strongest chemical symbol on this list.
What it means
In the Globally Harmonized System, the skull and crossbones is pictogram GHS06, acute toxicity (fatal or toxic). It sits inside a red diamond border on a white background. It is one of the nine GHS pictograms that OSHA's Hazard Communication Standard uses on chemical labels. The others cover flames, corrosion, gas cylinders, and similar hazards.
The symbol is not a general "bad" marker. It points to poisoning, so using it loosely weakens its meaning for the people who must react to it.
Reserve the skull for poison, because a symbol used everywhere warns about nothing.
Copy and paste
The character is U+2620, SKULL AND CROSSBONES. Pasted text carries no red diamond, so it works for notes and documents but not for compliance.
☠
☠
Where to use it
The supplier usually prints the GHS06 pictogram on the container, and you should keep that label legible. When you decant a toxic chemical, the secondary container needs its own hazard label. Fill it from the safety data sheet, not from memory.
- Chemical storage cabinets and rooms
- Pesticide and solvent containers
- Training material on hazard communication
3. Biohazard symbol for infectious material
The biohazard symbol warns of infectious agents, such as pathogens, blood-borne contamination, and medical waste. Its three-ring design is deliberately unlike any common shape.
What it means
The symbol marks materials that can spread disease to people. OSHA's bloodborne pathogens standard requires biohazard labels in fluorescent orange or orange-red. Laboratory entrance signs also use the symbol to show the biosafety level the space is authorized to handle, from BSL-1 to BSL-3.
Color matters here. A yellow or black version in a document is fine for information, but a regulated label has to follow the color rule.
If a label must be orange to be legal, a recolored version is a note and not a label.
Copy and paste
The character is U+2623, BIOHAZARD SIGN. It looks different from font to font, and some systems show it as a thin outline.
☣
☣
Where to use it
Place the symbol where people might touch infectious material, and keep it visible after cleaning and wear. Common spots include:
- Medical waste bins and sharps containers
- Refrigerators that hold blood or tissue samples
- Laboratory doors and specimen transport coolers
4. Radioactive trefoil for radiation
The trefoil marks radioactive material or a radiation area. Few symbols are as widely recognized, and few are as strictly controlled.
What it means
In the United States, the trefoil is traditionally magenta or purple on a yellow background. ISO 7010 lists the warning version as W003, radioactive material or ionizing radiation. The symbol tells people that exposure is possible and that they should follow the posted rules.
Radiation signs are regulated, and the wording that accompanies the trefoil, such as "Caution, Radioactive Material," depends on the type and amount of material. The symbol alone does not meet those requirements.
The trefoil starts the conversation, but the regulated wording finishes it.
Copy and paste
The character is U+2622, RADIOACTIVE SIGN. Many people also use it as a shorthand for "nuclear" in casual writing, so context decides how serious it reads.
☢
☢
Where to use it
Use the character in training and reference material. For real postings, follow the rules of the agency that licenses your material, and consult your radiation safety officer. Typical locations include:
- Imaging and treatment rooms
- Industrial gauges and sealed sources
- Storage and shipping areas for radioactive material
5. High voltage symbol for electrical shock
The high voltage symbol, a lightning bolt, warns that electric shock, burns, or arc flash are possible. It belongs on anything that carries enough energy to injure.
What it means
ISO 7010 lists the pictogram as W012, warning of electricity, a black bolt inside a yellow triangle. In the US, an equipment label often pairs a bolt with a DANGER header when contact can kill and a WARNING header for lesser exposure. Pick the header from the real risk and do not default to the loudest one.
Overusing red teaches workers to ignore it. Anything that is not a serious hazard should use the milder signal word.
Match the signal word to the real risk, because overused red stops getting noticed.
Copy and paste
The character is U+26A1, HIGH VOLTAGE SIGN. In chat, ⚡ usually means speed or energy, so do not rely on it alone for a digital safety message.
⚡
⚡
Where to use it
Put the bolt on electrical panels, transformers, junction boxes, battery rooms, and disconnects. Use a durable material and a size that someone can read from the distance they will approach.
Safety Decals sells a Danger decal in three listed sizes, from 11" W x 8.5" H up to 15" W x 11.6" H, priced from $10.99 to $35.99. Its material list includes reflective ORALITE® vinyl for low-light areas.
6. Construction sign for work zones
The construction sign, a striped barrier, marks an area where work is under way and the normal conditions do not apply. It signals a temporary hazard and not a permanent one.
What it means
The barrier tells people to slow down, stay out, or follow a detour. On US roads, temporary work zone signs are orange, while permanent hazard warnings use a yellow diamond. The same logic applies on a job site. Orange suggests something temporary is happening, and yellow suggests the hazard is part of the place.
Use it for the span of the work and take it down when the work ends. A barrier symbol left up for months teaches people to walk past it.
A work zone marker is only honest while the work is happening.
Copy and paste
The character is U+1F6A7, CONSTRUCTION SIGN, an emoji. Older systems and some fonts may show an empty box instead, so check the destination before you use it in a critical message.
🚧
🚧
Where to use it
Use 🚧 in status updates, project trackers, and maintenance notices to flag areas that are closed or changing. For physical spaces, pair a barrier with a sign that states the hazard.
The Safety Decals Caution Falling Hazard & Warning Tipping Hazard decal measures 5" W x 14" H and costs $8.99 to $14.99. It suits equipment and work areas where the hazard is specific and not general.
Pick the symbol that matches the hazard
Start with ⚠ when you need a general alert, then move to a specific symbol when the hazard has a name. Use ☠ for poison, ☣ for infectious material, ☢ for radiation, ⚡ for electricity, and 🚧 for temporary work areas. On screen, the character is enough. On a wall or a machine, the color, signal word, and size matter as much as the symbol.
If you need a physical version, Safety Decals can help you choose the right label and customize its size, design, colors, and material. Browse the hazard warning decals at Safety Decals, or email sales@safetydecals.com with the hazard you need to mark.
