Biological hazard

A biological hazard, or biohazard, is a biological substance that poses a threat to the health of living organisms, primarily humans. This could include a sample of a microorganism, virus or toxin that can adversely affect human health. A biohazard could also be a substance harmful to other animals.[lower-alpha 1]

The biohazard symbol

The term and its associated symbol are generally used as a warning, so that those potentially exposed to the substances will know to take precautions. The biohazard symbol was developed in 1966 by Charles Baldwin, an environmental-health engineer working for the Dow Chemical Company on the containment products.[1]

It is used in the labeling of biological materials that carry a significant health risk, including viral samples and used hypodermic needles.

In Unicode, the biohazard symbol is U+2623 ().

ANSI Z535/OSHA/ISO regulation

Biohazardous safety issues are identified with specified labels,[lower-alpha 2] signs and paragraphs established by the American National Standards Institute (ANSI). Today, ANSI Z535 standards for biohazards are used worldwide and should always be used appropriately within ANSI Z535 Hazardous Communications (HazCom) signage, labeling and paragraphs. The goal is to help workers rapidly identify the severity of a biohazard from a distance and through color and design standardization.

Biological hazard symbol design:

  • A red or white-colored background is used behind a black biohazard symbol when integrated with a DANGER sign, label or paragraph.
  • An orange or white-colored background is used behind a black biohazard symbol when integrated with a WARNING sign, label or paragraph.
  • A yellow or white-colored background is used behind a black biohazard symbol when integrated with a CAUTION sign, label or paragraph.
  • A light-blue or white-colored background is used behind a black biohazard symbol when integrated with a NOTICE sign, label or paragraph.

DANGER is used to identify a biohazard that will cause death. WARNING is used to identify a biohazard that may cause death. CAUTION is used to identify a biohazard that will cause injury, but not death. NOTICE is used to identify a non-injury biohazard message (e.g. hygiene, cleanup or general lab policies).

OSHA requires the use of proper ANSI HazCom where applicable in American workplaces. States and local governments also use these standards as codes and laws within their own jurisdictions. Proper use of ANSI Z535 signs, labels and paragraphs are written into many of OSHA's standards for HazCom and crafted to integrate with ISO symbols.

Reference ANSI Z535 for a complete description on how to use DANGER, WARNING, CAUTION and NOTICE signs, labels or paragraphs.

UN/ISO Classification

Biohazardous agents are classified for transportation by UN number:[2]

  • Category A, UN 2814 – Infectious substance, affecting humans: An infectious substance in a form capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals when exposure to it occurs.
  • Category A, UN 2900 – Infectious substance, affecting animals (only): An infectious substance that is not in a form generally capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans and animals when exposure to themselves occurs.
  • Category B, UN 3373 – Biological substance transported for diagnostic or investigative purposes.
  • Regulated Medical Waste, UN 3291 – Waste or reusable material derived from medical treatment of an animal or human, or from biomedical research, which includes the production and testing.

Levels of biohazard

Immediate disposal of used needles into a sharps container is standard procedure.
NHS medics practice using protective equipment used when treating Ebola patients

The United States Centers for Disease Control and Prevention (CDC) categorizes various diseases in levels of biohazard, Level 1 being minimum risk and Level 4 being extreme risk. Laboratories and other facilities are categorized as BSL (Biosafety Level) 1–4 or as P1 through P4 for short (Pathogen or Protection Level).

  • Biohazard Level 1: Bacteria and viruses including Bacillus subtilis, canine hepatitis, Escherichia coli, and varicella (chickenpox), as well as some cell cultures and non-infectious bacteria. At this level precautions against the biohazardous materials in question are minimal, most likely involving gloves and some sort of facial protection.
  • Biohazard Level 2: Bacteria and viruses that cause only mild disease to humans, or are difficult to contract via aerosol in a lab setting, such as hepatitis A, B, and C, some influenza A strains, Human respiratory syncytial virus, Lyme disease, salmonella, mumps, measles, scrapie, dengue fever, and HIV. Routine diagnostic work with clinical specimens can be done safely at Biosafety Level 2, using Biosafety Level 2 practices and procedures. Research work (including co-cultivation, virus replication studies, or manipulations involving concentrated virus) can be done in a BSL-2 (P2) facility, using BSL-3 practices and procedures.
  • Biohazard Level 3: Bacteria and viruses that can cause severe to fatal disease in humans, but for which vaccines or other treatments exist, such as anthrax, West Nile virus, Venezuelan equine encephalitis, SARS coronavirus, MERS coronavirus, SARS-CoV-2, Influenza A H5N1, hantaviruses, tuberculosis, typhus, Rift Valley fever, Rocky Mountain spotted fever, yellow fever, and malaria.
  • Biohazard Level 4: Viruses that cause severe to fatal disease in humans, and for which vaccines or other treatments are not available, such as Bolivian hemorrhagic fever, Marburg virus, Ebola virus, Lassa fever virus, Crimean–Congo hemorrhagic fever, and other hemorrhagic diseases, as well as Nipah virus.[3] Variola virus (smallpox) is an agent that is worked with at BSL-4 despite the existence of a vaccine, as it has been eradicated and thus the general population is no longer routinely vaccinated. When dealing with biological hazards at this level, the use of a positive pressure personnel suit with a segregated air supply is mandatory. The entrance and exit of a Level Four biolab will contain multiple showers, a vacuum room, an ultraviolet light room, autonomous detection system, and other safety precautions designed to destroy all traces of the biohazard. Multiple airlocks are employed and are electronically secured to prevent doors from both opening at the same time. All air and water service going to and coming from a Biosafety Level 4 (P4) lab will undergo similar decontamination procedures to eliminate the possibility of an accidental release. Currently there are no bacteria classified at this level.


Biological hazard
In UnicodeU+2623 BIOHAZARD SIGN (HTML ☣)

The biohazard symbol was developed by the Dow Chemical Company in 1966 for their containment products.[1] According to Charles Baldwin,[1] 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." In an article he wrote for Science in 1967,[4] the symbol was presented as the new standard for all biological hazards ("biohazards"). The article explained that over 40 symbols were drawn up by Dow artists, and all of the symbols investigated had to meet a number of criteria:

  1. Striking in form in order to draw immediate attention;
  2. Unique and unambiguous, in order not to be confused with symbols used for other purposes;
  3. Quickly recognizable and easily recalled;
  4. Symmetric, in order to appear identical from all angles of approach;
  5. Acceptable to groups of varying ethnic backgrounds.

The chosen symbol scored the best on nationwide testing for memorability.[5]

The design was first specified in 39 FR 23680 but was dropped in the succeeding amendment. However, various US states adopted the specification for their state code.[6]

See also

  • Anthropogenic hazard  Hazard caused by human action or inaction
  • Biocontainment  Physical containment of pathogenic organisms or agents in microbiology laboratories
  • Biological agent  Pathogen that can be weaponized
  • Biosafety level  Level of the biocontainment precautions required to isolate dangerous biological agents
  • Chemical hazard  Non-biological substance that has the potential to cause harm to life or health
  • Hazard  Substance or situation which has the potential to cause harm to health, life, the environment, property, or any other value
  • Health hazard
  • Interplanetary contamination  Biological contamination of a planetary body by a space probe or spacecraft
  • List of laboratory biosecurity incidents
  • Mechanical hazard  Hazard with a mechanical energy source
  • Occupational hazard  Hazard experienced in the workplace
  • Physical hazard  Hazard due to a physical agent
  • Planetary protection  Guiding principle in the design of an interplanetary mission, aiming to prevent biological contamination of both the target celestial body and the Earth
  • Psychosocial hazard  Occupational hazard to one's psychological well-being
  • Public health  Preventing disease, prolonging life and promoting health through organized efforts and informed choices of society and individuals


  1. See Classification, "Category A, UN 2900"
  2. See Globally Harmonized System of Classification and Labelling of Chemicals for chemical labeling standards for containers.


  1. "Biohazard Symbol History". Archived from the original on February 13, 2012.
  2. "USDA Policies and Procedures on Biohazardous Waste Decontamination, Management, and Quality Controls at Laboratories and Technical Facilities". USDA. Archived from the original on March 5, 2017. Retrieved December 17, 2016.
  3. Tigabu, Bersabeh; Rasmussen, Lynn; White, E. Lucile; Tower, Nichole; Saeed, Mohammad; Bukreyev, Alexander; Rockx, Barry; LeDuc, James W.; Noah, James W. (1 April 2014). "A BSL-4 High-Throughput Screen Identifies Sulfonamide Inhibitors of Nipah Virus". Assay and Drug Development Technologies. 12 (3): 155–161. doi:10.1089/adt.2013.567. PMC 3994909. PMID 24735442.
  4. "BIOHAZARD SYMBOL: WHAT DOES IT MEAN?". The IDC Medical, Australia. Retrieved 2021-06-17.
  5. Baldwin, C. L.; Runkle, R. S. (13 October 1967). "Biohazards Symbol: Development of a Biological Hazards Warning Signal". Science. 158 (3798): 264–265. Bibcode:1967Sci...158..264B. doi:10.1126/science.158.3798.264. PMID 6053882.
  6. WAC 296-800-11045 Archived February 10, 2012, at the Wayback Machine, see PDF for a high resolution graphic


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