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A trefoil of overlapping circles, designed to be instantly recognisable as a warning for biological hazards.
Also known as: Biohazard sign, ISO 7010 W009, Biological hazard sign
Designed in 1966 by Dow Chemical Company engineers for their containment products, the biohazard symbol was deliberately created to be highly memorable but symbolically meaningless, so its warning association could be taught rather than assumed. It became a US and international standard for labelling biological hazards.
Deliberately designed in 1966 to have no pre-existing visual associations, so its warning meaning could be taught cleanly through public education rather than relying on the shape's own connotations — described by its designers as 'memorable but meaningless'.
1966
Is registered in ISO 7010 as W009, warning: biological hazard, and is drawn as three broken rings overlapping a central circle — a shape chosen in the 1960s precisely because it resembled nothing already in use and so could not be mistaken for a symbol somebody already half-knew.
Contexts: Medicine, Laboratory
Is seen on sharps bins and clinical-waste bags, on containment laboratory doors, on specimen transport packaging and on autoclave bags. On a waste container it is an instruction about disposal route, not a claim that the contents are infectious.
Contexts: Packaging, Medicine, Laboratory
Three identical crescent-and-circle shapes arranged around a small central circle, radially symmetric so it reads the same from any angle.
Three broken rings around a circle is biological; three solid blades around a disc is radiation.
Both are internationally recognised hazard-warning trefoils, though for different hazard types and standards bodies.