Hazard symbol

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File:Skull and crossbones.svg

Hazard symbols are easily recognizable symbols designed to warn about hazardous materials or locations. The use of hazard symbols is often regulated by law and directed by standards organizations. Hazard symbols may appear with different colors, backgrounds, borders and supplemental information in order to signify the type of hazard.

Common hazard symbols

Name Symbol Unicode Image
Toxic sign U+2620 File:Skull and crossbones.svg
Caution sign U+2621
Radiation sign U+2622 Radioactivity
Ionizing radiation sign File:New radiation symbol ISO 21482.svg
Non-ionizing radiation sign radiowave
Biohazard sign U+2623 Biohazard
Warning sign U+26A0 Warning
High voltage sign U+26A1 High voltage

Radioactive sign


The international radiation symbol (also known as trefoil) first appeared in 1946, at the University of California, Berkeley Radiation Laboratory. At the time, it was rendered as magenta, and was set on a blue background.[1] It is drawn with a central circle of radius R, an internal radius of 1.5R and an external radius of 5R for the blades, which are separated from each other by 60°.[2]

File:New radiation symbol ISO 21482.svg On February 15, 2007, the IAEA and the ISO announced this new ionizing radiation symbol to supplement the traditional trefoil symbol. The new symbol is aimed at alerting anyone, anywhere to the potential dangers of being close to a large source of ionizing radiation. [3] X


Biohazard sign

Developed by Dow Chemical company in the 1960s for their containment products.[4]

According to Charles Dullin, an environmental-health engineer who contributed to its development:

We wanted something that was memorable but meaningless, so we could educate people as to what it means.


All parts of the Biohazard sign can be drawn with a compass and/or ruler. The basic outline of the symbol is a plain trefoil, which is three circles overlapping each other equally like in a triple venn diagram with the overlapping parts erased. The diameter of the overlapping part is equal to half the radius of the three circles. Then three inner circles are drawn in with 2/3 radius of the original circles so that it's little tangent to the outside three overlapping circles. A tiny circle in center has a diameter 1/2 of the radius of the three inner circle, and arcs are erased at 90°, 210°, 330°. The arcs of the inner circles and the tiny circle are connected by a line. Finally, the ring under is drawn from the distance to the perimeter of the equilateral triangle that forms between the centers of the three intersecting circles. An outer circle of the ring under is drawn and finally enclosed with the arcs from the center of the inner circles with a shorter radius from the inner circles.[5]


Toxic sign

File:Skull and crossbones.svg The skull and crossbones symbol, consisting of a human skull and two bones crossed together under the skull, is today generally used as a warning of danger, particularly in regard to poisonous substances.

The symbol, or some variation thereof, was also featured on the Jolly Roger, the traditional flag of European and American pirates. It is also used by the Skull and Bones, a secret society at Yale University, and is part of the WHMIS home symbols placed on containers to confirm that the substance inside is dangerous in a way.

In the USA, due to concerns that the skull and bones symbol's association with pirates encourages children to play with toxic materials, the Mr. Yuk symbol is also used to denote poison.

Warning sign

On warning signs, an exclamation mark is often used to draw attention to a warning of danger, hazards and the unexpected.There are several theories about the origins of the exclamation mark.

Chemical hazard

NFPA 704 standard hazard sticker or placard. See NFPA 704 for details.
File:Tablica ADR.svg
European hazard sign, saying highly inflammable (33) - gasoline (1203)

A chemical hazard label is a pictogram applied to containers of dangerous chemical compounds to indicate the specific risk, and thus the required precautions. There are several systems of labels.

The U.S.-based National Fire Protection Association (NFPA) has a standard NFPA 704 using a diamond with four colored sections each with a number indicating severity 0-4 (0 for no hazard, 4 indicates a severe hazard). The red section denotes flammability. Blue is health risks. Yellow is reactivity (tendency to explode). The white section denotes special hazard information. This label is used primarily in the USA.

In Europe, another standard is used, as fixed in the ADR-Agreement. Vehicles carrying dangerous goods have to be fitted with orange signs, where the lower number identifies the substance, while the upper number is a key for the threat it may pose.

European hazard symbols

These hazard symbols for chemicals are defined in Annex II of Directive 67/548/EEC. A consolidated list with translations into other EU languages can be found in Directive 2001/59/EC (See the links section).

The 'n' in Harmful (Xn) stands for the French word nocif (noxious).

See also


  1. "Origin of the Radiation Warning Symbol (Trefoil)". 
  2. "Biohazard and radioactive Symbol ,design and proportions" (PDF). 
  3. This symbol is included in ISO 21482:2007. ISO International Standards are protected by copyright and may be purchased from ISO or its members (please visit www.iso.org for more information). ISO has not reviewed the accuracy or veracity of this information. "New Symbol Launched to Warn Public About Radiation Dangers". Retrieved 2007-02-15. 
  4. "Biohazard Symbol History". 
  5. "Biohazard and radioactive Symbol ,design and proportions" (PDF). 

External links

Wikimedia Commons has media related to:

bg:Международни символи за химична опасност ca:Símbols de perillositat de:Gefahrensymbol it:Simboli di rischio chimico ku:Nîşanên xeterê no:Faresymboler sv:Farosymbol