Biohazards, also known as biological hazards, are biological substances that pose a health hazard to humans, animals, and the environment more generally. Biohazardous pathogens include:

  • Viruses
  • Bacteria
  • Other microorganisms
  • Toxins derived from a biological source

A warning sign, the standard biohazard symbol, was designed and adapted to warn about the existence of biological hazards.

The Development and Implementation of the Biohazard Symbol

As referenced a moment ago, the biohazard symbol exists to warn people to take precautions to prevent exposure to biohazardous substances.

Prior to 1966, there existed a myriad of different types of biohazard warning signs. The reality was few people knew what was meant by the different biohazard warning signs that were then in existence. An environmental and health engineer named Charles Baldwin became particularly concerned about this mish-mash of purported biohazard warning signs.

He determined that one uniform, standardized biohazard warning sign of some type was the proper course to take. By taking this approach, Baldwin argued that the general public and others would better be protected against the potential risks presented by biohazardous materials.

Baldwin was employed by Dow Chemical Company, an enterprise quite familiar with bio- and other types of hazards. Baldwin turned to the Dow Company packaging design team to come up with a standardized biological hazard warning symbol. According to Baldwin, his instructions to the designed team were simple. “The only guidance I gave them to noodle through were, it must be unique and something that would be striking enough that it would be remembered. We wanted to develop something that was memorable and meaningful to educate people about what it means.” Baldwin said.

Working with the design team, a list of criteria was delineated for the final design:

  • Striking design
  • Unique and unambiguous
  • Draws immediate attention
  • Not confused with other symbols
  • Quickly recognizable
  • Readily recalled
  • Easily stenciled
  • Symmetric (to appear identical from all angles)
  • Acceptable to groups of varying ethnic backgrounds

Over 40 symbols were designed in the process. Nationwide testing was performed on the various symbols. In the end, the biohazard warning symbol used today outpaced the other designs. This particularly was the case when it came to memorability, a truly important consideration. Time and again, the biohazard symbol in use ever since that time was the one more remembered by consumer testing participants. By 1967, the biohazard symbol still ubiquitously in use today was selected.

The Meaning of the Four Circles in the Biohazard Symbol

The biohazard symbol adopted in the 1960s, and still in use today, has four circles. These circles have specific meanings. The four circles contained within the biohazard symbol represent the chain of infection:

  • Agent: The type of pathogen, that causes an infection or a hazardous condition.
  • Host: The organism the pathogen infects.
  • Source: The host from which the pathogen originated.
  • Transmission: The means of pathogen transmission, mostly direct or indirect. (Some routes of transmission may include air, insect bite, and contaminated surfaces.)

Utilized for All Biohazard Levels

In order to optimize safety, the biohazard symbol is utilized for all four levels of biohazards established by the U.S. Centers for Disease Control and Prevention, and via similar agencies in other nations across the globe. These four biohazard levels are:

  • Biohazard Level 1: Bacteria and viruses that pose a more minimal threat to human health.
  • Biohazard Level 2: Bacteria and viruses that cause only mild disease in humans.
  • Biohazard Level 3: Bacteria and viruses that can cause severe to fatal disease in humans, but for which vaccines or other treatments exist.
  • Biohazard Level 4: Viruses that cause severe to fatal disease in humans, and for which no vaccines or other treatments are available.

International Adoption of Biohazard Symbol

When the biohazard symbol that grew out of the work of people at Dow Chemical Company was adopted for use in the United States, it quickly became the international warning device. The symbol is in use in all countries across the globe today.

Two primary reasons exist for the rapid international adoption of the biohazard symbol from the Dow team. First, the design of the symbol renders it highly effective when it comes to warning people of the existence of a biohazard. Second, because the United States, and its major international trading partners, were quick to adopt and utilize the symbol, other nations followed suit to maintain efficiently managed trading relationships with the U.S.A and its major trading partners.

The fact that the biohazard warning symbol was the brainchild of the Dow Chemical Company also added to its rapid international adoption. Dow was and remains a multinational enterprise. It was and remains one of the three largest chemical companies in the world.

Photo Courtesy of Tom Woodward.


Emily Kil

Co-Owner of Eco Bear Biohazard Cleaning Company

Together with her husband, Emily Kil is co-owner of Eco Bear, a leading biohazard remediation company in Southern California. An experienced entrepreneur, Emily assisted in founding Eco Bear as a means of combining her business experience with her desire to provide assistance to people facing challenging circumstances. Emily regularly writes about her first-hand experiences providing services like biohazard cleanup, suicide cleanup, crime scene cleanup, unattended death cleanup, and other types of difficult remediations in homes and businesses.