Biohazard Symbol

The biohazard symbol (☣, U+2623) marks anything biologically dangerous — contaminated waste, infectious samples, quarantine zones. Unlike most hazard signs, which evolved slowly from older pictograms, this one was built from scratch in a single 1966 design project with an unusual brief: make it stick in people's memory before they even know what it means.

Most hazard symbols evolved gradually — the biohazard sign was engineered in a single project. In 1966, Dow Chemical environmental health engineer Charles Baldwin and the National Institutes of Health's Robert S. Runkle set out to fix a real problem: there was no shared symbol for biological hazards, so different organizations improvised their own. The U.S. Navy used a pink rectangle, the Army an inverted blue triangle, the Postal Service a staff-and-snake design on violet — none of it recognizable across organizations, let alone to the public.

Their brief, published in Science that year, was unusual: they wanted a symbol that was "memorable but meaningless, so we could educate people as to what it means" — the opposite of reusing an existing icon whose prior associations might mislead. Baldwin's team tested a range of candidate designs for how well people could recall them and how little existing meaning people projected onto them. The trefoil-and-circles design that became ☣ scored highest on memorability and lowest on meaningfulness of everything tested, and it was adopted as the U.S. biohazard standard shortly after.

The character entered Unicode in version 1.1 (1993) as a plain black-and-white glyph, and became a full-color emoji in Emoji 1.0 (2015). Outside labs and hazmat labeling, it's since picked up a second life in gaming and social bios — often to jokingly mark something "contaminated" or a source of bad vibes, a meaning nobody in that 1966 design brief could have anticipated.