What the biohazard symbol means
The biohazard symbol ☣︎ warns of biological hazards: bacteria, viruses, blood, medical waste and other living materials that can make people sick. You see it on hospital sharps containers, lab freezers, medical waste bags and the doors of labs that handle infectious agents.
Labs that work with these materials are graded by biosafety level, from BSL-1 for low-risk microbes to BSL-4 for the most dangerous pathogens, and the ☣︎ sign is posted at the entrance. On labels it is usually printed in black on a bright orange, orange-red or yellow background so it stands out.
Who designed it
The symbol was created in 1966 by Charles Baldwin, an environmental-health engineer at Dow Chemical. The goal was a shape that was striking and easy to remember but did not already mean anything, so people would learn it purely as a warning. Its three crescents around a small circle give it three-way symmetry, so it reads the same when rotated.
Don't confuse it with the radiation trefoil ☢︎, which has three solid blades around a dot and warns about ionizing radiation, or with the poison skull ☠︎ on the toxic symbol page.
How to type ☣︎
In Microsoft Word, type 2623 and press Alt + X. In HTML, use ☣. On phones, search the emoji keyboard for "biohazard". On Windows, press Windows + ., and on a Mac press Control + Command + Space and search for biohazard. The character has been in Unicode since version 1.1 in 1993, so even old systems can show its text form.
Gamers and fans of zombie and post-apocalyptic stories also use ☣︎ in clan tags and usernames. Combine it with ☢︎ or ⚠︎ for a full hazard look, or browse all warning symbols and the caution symbol.