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The international symbol for biological hazard.

A biological hazard or biohazard is an organism, or substance derived from an organism, that poses a threat to (primarily) human health. This can include medical waste or samples of a microorganism, virus or toxin (from a biological source) that can impact human health. It can also include substances harmful to animals. The term and its associated symbol is generally used as a warning, so that those potentially exposed to the substances will know to take precautions.

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

Biohazardous agents are classified for transportation by UN number:

  • UN 2814 (Infectious Substance, Affecting Humans)
  • UN 2900 (Infectious Substance, Affecting Animals)
  • UN 3373 (Diagnostic Specimen or Clinical Specimen or Biological Substance, Category B)
  • UN 3291 (Medical Waste)


Levels of biohazard

Immediate disposal of used needles into a sharps container is standard procedure.

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.

  • Biohazard Level 1: Bacteria and viruses including Bacillus subtilis, canine hepatitis, Escherichia coli, varicella (chicken pox), 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. Usually, contaminated materials are left in open (but separately indicated) waste receptacles. Decontamination procedures for this level are similar in most respects to modern precautions against everyday viruses (i.e.: washing one's hands with anti-bacterial soap, washing all exposed surfaces of the lab with disinfectants, etc). In a lab environment, all materials used for cell and/or bacteria cultures are decontaminated via autoclave.
  • 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, influenza A, 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 facility, using BSL-3 practices and procedures. Virus production activities, including virus concentrations, require a BSL-3 facility and use of BSL-3 practices and procedures", see Recommended Biosafety Levels for Infectious Agents[1].

See also





  • Baldwin, C. L., & Runkle, R.S. (1967). Biohazards symbol: development of a biological hazards warning signal. Science, 158, 264–265. Pubmed unique identifier 6053882.
  • Preston, Richard. (1994). The Hot Zone. Anchor Books: Division of Random House; New York.
  • Preston, Richard. (2002). The Demon in the Freezer: A True Story. of Random House; New York.

External links

Simple English

A biological hazard, or biohazard, is anything coming from living organisms (ie. pollen, fungi, animals, insects, bacteria and viruses) that could be a threat to someone's health. It is represented by ☣, the biohazard symbol, which is used everywhere in the world. When people see this sign they know to take precautions, and to follow proper conduct for science labs.

Biosafety levels

There are four biosafety levels made by the Center of Disease Control. These are used in laboratories so only people who have the right skills can enter. Different levels mean scientists must wear different uniforms and take special care when dealing with dangerous things like viruses.

Biosafety Level 1 The viruses handled in BSL-1 are not very dangerous and usually only cause mild sickness. Diseases in BSL-1 include chicken pox and some E-Coli strains. People in BSL-1 have to wash their hands with soap, wear gloves, and put waste materials in specially-marked bins.

Biosafety Level 2 BSL-2 is filled with slightly more hazourdous diseases than BSL-1. They have to take more safety precautions has a result. Hepatitis, influenza, HIV / AIDS, and salmonella are handled here.

Biosafety Level 3 BSL-3 is for diseases that may kill but are less deadly than those in Level 4, SARS and yellow fever. A lot of them are airborne, and the lab must be in an closed off area in case of an incident.

Biosafety Level 4 BSL-4 is for very hazardous diseases that kill many people and are hard to treat. BSL-4 workers must be careful and alert at all times and wear suits with special air filters. A lot of hemorrhagic fevers are dealt with in BSL-4, like Ebola, Marburg, and Lassa Virus.


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