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Short answer: laboratory safety symbols are the pictograms, words and colors on signs that warn people about hazards in a lab. Under OSHA’s accident prevention sign rule, 29 CFR 1910.145, a sign falls into one of a few classes: danger (red, black and white), caution (yellow and black), safety instruction (white and green), or biological hazard. The rule’s recommended color-coding appendix gives fluorescent orange or orange-red for biological hazard tags under 1910.145(f); the biological hazard sign provision, 1910.145(e)(4), defines the warning but states no color. The class tells a reader how urgent the message is; the symbol tells them what the hazard is.
What is a laboratory safety symbol?
A lab symbol, or laboratory symbol, is the graphic part of a safety sign: a biohazard trefoil, a flame, a laser burst, a hand-wash figure. It sits on a sign next to a signal word and short wording. Which regulatory class a sign belongs to decides its color, its wording and when it may be used, so this guide sorts lab symbols by class.
This guide covers the signs posted on doors, walls and equipment. It does not cover the pictograms printed on chemical container labels, which follow the Globally Harmonized System and are explained in a separate guide: GHS labels, pictograms, signal words and hazard statements.
Sign classes and colors under 29 CFR 1910.145
Safety signs in laboratories sit under the general accident prevention sign standard, 29 CFR 1910.145 (Legal Information Institute copy of the e-CFR, checked 2026-10-29). It sorts signs by use, and sets the colors for each class by reference to the ANSI Z53.1-1967 or ANSI Z535.1-2006(R2011) safety-color specifications.
| Sign class | What the rule says it is for | Colors in 1910.145 |
|---|---|---|
| Danger | Employees are to be instructed that danger signs indicate immediate danger and that special precautions are necessary. There shall be no variation in the type of design of signs posted to warn of specific dangers and radiation hazards. | Red, black and white |
| Caution | Used only to warn against potential hazards or to caution against unsafe practices. | Yellow background; black panel with yellow letters; letters on the yellow background are black |
| Safety instruction | Used where there is a need for general instructions and suggestions relative to safety measures. | White background; green panel with white letters; letters on the white background are black |
| Biological hazard | Signifies the actual or potential presence of a biohazard and identifies equipment, containers, rooms, materials, experimental animals, or combinations of these that contain or are contaminated with viable hazardous agents. | No color stated in 1910.145(e)(4); the recommended orange or orange-red coding in the appendix to 1910.145(f) applies to biological hazard tags |
Danger versus caution
The rule draws the line between an immediate danger and a potential hazard. A danger sign means immediate danger; a caution sign is for potential hazards or unsafe practices. A caution sign is therefore not a softer way to mark an immediate hazard, and the standard says caution signs are used only for the potential-hazard case.
Biohazard symbol
The biohazard warning is a defined sign type in its own right. It marks equipment, containers, rooms, materials and experimental animals that contain or are contaminated with viable infectious agents presenting a risk to people. For the room-level containment context behind those signs, see biosafety levels BSL-1 to BSL-4, and for waste containers, biohazard bag and container requirements.
Radiation and other special hazards
For radiation hazards the rule requires that there be no variation in the type of design of signs posted to warn of them. Laser areas are covered by separate laser-specific guidance; see laser safety classes.
Sign, label and tag: which does what
People often use the three words interchangeably, but the OSHA text treats them as different tools.
| Item | What the source says |
|---|---|
| Sign | A posted, classed warning (danger, caution, safety instruction, biological hazard) under 1910.145. Wording should be easily read and concise, make a positive rather than negative suggestion, and be accurate in fact. |
| Tag | A temporary warning. Tags are used to prevent injury from hazardous conditions, equipment or operations that are out of the ordinary, unexpected or not readily apparent, and stay in use until the hazard is eliminated or the operation is completed. Danger tags are for major hazard situations where an immediate hazard threatens death or serious injury; caution tags are for minor hazard situations presenting a lesser threat of injury. Tags need not be used where signs, guarding or other positive means of protection are being used. |
| Chemical container label | Under the OSHA Laboratory Standard, 29 CFR 1910.1450(h)(1)(i), employers shall ensure that labels on incoming containers of hazardous chemicals are not removed or defaced (Legal Information Institute copy, checked 2026-10-29). |
A related placard, the NFPA 704 diamond, is compared with GHS labels in NFPA 704 fire diamond vs GHS labels.
Where signs matter for labs and facilities
What the Laboratory Standard recommends
The Laboratory Standard’s non-mandatory Appendix A lists signs that should be posted, including emergency telephone numbers, location signs for safety showers, eyewash stations, other safety and first aid equipment and exits, and warnings at areas or equipment where special or unusual hazards exist. The text of the standard itself does not go further than that, so a lab’s own written program and its institutional safety office decide which signs go where.
A short audit checklist for signage
Each item below traces to the sign rule’s wording requirements and class definitions; use it alongside the laboratory safety self-inspection checklist, which has its own labeling and signage section.
- Is each sign in the right class for the message: danger for an immediate hazard, caution for a potential hazard or unsafe practice, safety instruction for general instruction?
- Do the colors match the class (red, black and white for danger; yellow and black for caution; white and green for safety instruction)?
- Is the wording easily read and concise, and is it accurate in fact?
- Does the wording suggest what to do rather than only what not to do?
- Is every biohazard location (equipment, containers, rooms, animals) marked with the biohazard warning?
- Are temporary conditions handled with tags that come down once the hazard is eliminated?
Common misunderstandings
- “Safety symbols” and GHS pictograms are the same thing. They are not. GHS pictograms belong to container labels and safety data sheets; the signs in this guide are posted warnings governed by 1910.145.
- Yellow always means a lower-risk sign. Yellow is the caution class, reserved for potential hazards or unsafe practices. An immediate hazard belongs to the danger class.
- The Laboratory Standard requires a specific list of signs. Its recommended Appendix A language says prominent signs should be posted, including warnings where special or unusual hazards exist; it does not list every sign a lab must display.
- A tag replaces a sign. Tags are temporary and are not required where signs, guarding or other positive protection are in place.
FAQ
What are the main laboratory safety symbols?
Under 1910.145 the main sign classes are danger, caution, safety instruction and biological hazard, with colors set for the danger, caution and safety instruction classes. Within those classes labs use symbols for specific hazards such as biohazards and radiation.
What color is a biohazard sign?
The biological hazard sign provision, 1910.145(e)(4), defines the warning but does not state a color. The recommended (non-mandatory) color-coding appendix to 1910.145(f) gives fluorescent orange or orange-red, or predominantly so, for biological hazard tags.
What is the difference between a danger sign and a caution sign?
A danger sign indicates immediate danger and that special precautions are necessary. A caution sign is used only to warn against potential hazards or to caution against unsafe practices.
Are lab symbols on doors the same as the pictograms on chemical bottles?
No. Chemical bottle pictograms follow the GHS label system; door and equipment signs follow the sign classes above.
Sources
- OSHA, 29 CFR 1910.145, Specifications for accident prevention signs and tags (Legal Information Institute copy), checked 2026-10-29: https://www.law.cornell.edu/cfr/text/29/1910.145
- OSHA, 29 CFR 1910.1450, Occupational exposure to hazardous chemicals in laboratories (Legal Information Institute copy), checked 2026-10-29: https://www.law.cornell.edu/cfr/text/29/1910.1450
