The biological hazard-sign


Developed by the Dow Chemical company in 1966 for their containment products.

According to Charles Baldwin, 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 straightedge. 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 diameterof 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.

wikipedia biohazard sign

wikipedia biohazard


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