Microbiology is the study of tiny, microscopic organisms called microbes.[1] For studies like learning the shape and size of organisms, microscopic study is the preferable approach. However, when it comes to genetic analysis, molecular functions, and metabolic studies, the microbes are required to be cultured in labs in their preferable environment.

To ensure a particular strain of microbe is maintained in the cultures, strict aseptic or sterile conditions are required to be maintained in the labs. Moreover, people working in these labs also have a high likelihood of contracting diseases and infections caused by cultured microbes

Therefore, standard practices exist to ensure a safe work environment for people and the containment of the microbe inside the labs. These practices came into existence when scientists noted that there was a history of people contracting diseases, such as typhoid, tetanus, and cholera, that were associated with laboratories. 

Some of these reports include the[2]:

  • Sulkin and Pike (1949) report: Here, 21 of the 222 reported viral infections were considered to be serious and a third of the infection was attributed to poor handling of infected tissues.
  • Hanson et al (1967) report which links Arboviruses to 428 laboratory-associated infections and the commonest infection source in labs was infectious aerosols.
  • Skinhoj (1974) report on a survey of Danish clinical chemistry labs, where around 1000 lab personnel contracted hepatitis in a year. 

These studies emphasized the importance of learning and implementing biosafety measures in microbiology labs, especially while working with life-threatening microbes, such as viruses.

Principles of Biosafety

Several safe methods are available today that allow for better containment of microbes in labs, maintain their favorable environment, and prevent lab personnel from becoming infected with these infectious agents. This complete process is known as the containment of microbes and it’s divided into two[2]:

  • Primary containment: Here, personnel and the immediate laboratory environment are safeguarded from infectious agents. Primary containment is done by utilizing good microbiological techniques, proper safety equipment, and vaccinating working professionals in the labs.
  • Secondary containment: It’s the process of protecting the environment outside of the lab from the spread of infectious agents. This is done by combining highly-advanced designs of facilities with best operational practices.

Elements of Microbial Containment

The containment of microbes is composed of three elements: safety equipment, best laboratory practices and techniques, and facility design.

1. Safety Equipment

It’s also called the primary barrier which includes biosafety cabinets and a variety of other enclosed containers. The biosafety cabinet is beneficial to contain infectious aerosols, which are generated while performing microbiological procedures. 

The biosafety cabinets are categorized into three groups: Class I, Class II, and Class III biosafety cabinets. 

Class I and class II biosafety cabinets are open-fronted biological safety cabinets, thus they only offer partial containment. Class III biosafety cabinets provide maximum protection level to both laboratory personnel and the environment.

Other than biosafety cabinets, some other equipment, such as gloves, lab coats, shoe covers, lab gowns, face shields, respirators, boots, and safety glasses provide an extra level of protection to lab personnel.[2]

2. Best laboratory practices and techniques

Standard laboratory training and practices are essential for the containment of microbial organisms in labs. Lab personnel should be aware of the potential hazards of infected materials and agents they are required to work with. They must be taught standard practices and microbiological techniques for handling and maintaining such materials.

The lab director has an important role to play when it comes to choosing appropriate training for lab personnel. Moreover, when the safety measures and training are not sufficient to contain the spread of infectious agents, they are required to select additional practices to minimize/eliminate hazards associated with infectious materials/agents.

Additionally, a biosafety operation manual should be available in all labs explaining the hazards associated with each infectious agent and the procedures to minimize the risks. 

A lab expert or scientist trained in using laboratory techniques, aware of lab safety measures, and hazards associated with working with an infectious agent must direct such lab activities.[2]

3. Facility design

Appropriate facility design and engineering need to supplement lab personnel’s efforts, techniques, and best safety practices for proper containment and safety of people, inside or outside the labs. It serves as an additional barrier against the spread of infectious agents.

Based on the level of containment, the facility design is of three types[2]:

  • The basic laboratory

It includes the space created for working with viable infectious agents or materials that are not infectious or potentially have low levels of hazard, with biosafety level 1 and level 2 facilities.

For example, the locations of animal rooms and waste staging areas, which are known to be sources of general contamination, should not be adjacent to patient care areas, but they can be in the same building or complex.

Moreover, it is important to separate the public areas and offices needed by non-laboratory staff from the laboratories.

  • The containment laboratory

The containment lab contains some specialized engineering features to deal with potential hazards and protect lab personnel, the environment, and the community. It’s described as a biosafety level 3 facility.

Its access controls and specialized ventilation system are the distinguishing features of the containment lab.

The lab settings can be the building itself, a single module within it, or a complex of modules. And regardless of the situation, the laboratory is always separated from public areas by a controlled access zone.

  • The maximum containment laboratory

This lab has special engineering and containment systems. It permits the safe handling of infectious agents that can be extremely dangerous to lab workers or can cause epidemic diseases. This level of facility is described as biosafety level 4.

The lab should be built in isolated areas within the building or a separate building. It has secondary barriers to protect the environment from hazardous materials. 

The barrier can be airlocks or liquid disinfectant barriers, sealed entrances to the laboratory, a treatment system to eliminate contaminants from exhaust air, and a clothes-change room and a shower room adjacent to the laboratory ventilation system.

Four Biosafety Levels

Biosafety levels are divided into four levels based on their combination of safety equipment, laboratory techniques, best practices, and appropriate laboratory facilities to perform operations, control hazards by infectious agents, and run lab activities safely.

The combination of elements, designed and fit into these four levels decides the extent or degree of protection the labs provide to lab personnel, the environment, and the community.

The following is a brief overview of all four protection levels in ascending order.

Biosafety Level 1

The standard practices, equipment, and facilities included in this level suit undergraduate, secondary education training, or any other teaching labs or facilities where experiments are performed on viable microbial strains that don’t infect any healthy adult human. 

A few examples of these types of strains include Naegleria gruberi, Bacillus subtilis, and infectious canine hepatitis virus[2].

Even so, some opportunistic organisms can infect young, elderly, immunodeficient, or immunosuppressed individuals.

Standard microbiological practices:

  • When experiments are in progress, the laboratory director restricts or limits access as needed.
  • Decontamination is performed for all contaminated liquids and solids before disposal.
  • Once a day, work surfaces are decontaminated after a spill of any viable material.
  • To prevent contamination or soiling of street clothes, laboratory gowns, coats, or uniforms should be worn.
  • Prohibition of eating, drinking, smoking, storing food, and applying cosmetics inside the lab.
  • Pipetting is done with mechanical devices, and mouth pipetting is not permitted.

Special practices:

  • The decontaminated materials are placed in a leak-proof container before being taken away from the laboratory for decontamination.

Containment equipment:

  • Biosafety level 1 agents do not generally require special containment equipment.

Laboratory facilities:

  • The lab is designed to be easy to clean.
  • Each laboratory is equipped with a sink for handwashing.
  • A benchtop should be resistant to water, alkali, organic solvents, acid, and moderate heat.

Biosafety Level 2

The biosafety level 2 practices and equipment are suitable for diagnostic, clinical, and facilities that work with a wide range of indigenous moderate-risk infectious agents. 

These agents are generally associated with some human diseases with different degrees of severity. A few examples of the microbes in this category include salmonellae, Hepatitis B virus, and Toxoplasma spp[2].

Standard microbiological practices:

  • The standard microbiological practices of Biosafety Level 2 are similar to Biosafety Level 1.

Special practices:

  • The decontaminated materials are placed in a leak-proof container before being taken away from the laboratory for decontamination.
  • The lab director creates policies that ensure that only those who have been informed of potential hazards and meet entry requirements (e.g., immunizations) are allowed into the lab or animal rooms.
  • Rodent and insect control programs are in place.
  • Infectious material spills and accidents are immediately reported to the lab director. An appropriate medical evaluation, surveillance, and treatment are provided and records are maintained.

Containment equipment:

Lab personnel is required to use biosafety cabinets and personal protective equipment to perform lab procedures, especially when:

  • Working with a high concentration of infectious agents. These agents are required to be centrifuged in an open lab if using centrifuge safety cups and are only opened in biosafety cabinets.
  • Using a procedure with high potential to create aerosols.

Laboratory facilities:

The lab facilities are similar to Biosafety Level 1, except:

  • An autoclave is available for decontaminating infectious laboratory wastes.

Biosafety Level 3

This level of biosafety is applicable to research, teaching, diagnostic, clinical, and production facilities that work with indigenous or exotic agents, and where aerosols may pose a threat of infection and can have lethal consequences. 

Examples of agents for which biosafety level 3 is required include St. Louis encephalitis virus, Mycobacterium tuberculosis, and Coxiella burnetii[2].

Standard microbiological practices:

  • The standard microbiological practices of Biosafety Level 3 are similar to Biosafety Level 1.

Special practices:

In addition to the practices mentioned in Biosafety Level 2, it includes:

  • Lab doors should be closed while performing the experiments.
  • High-efficiency particulate air (HEPA) filters and liquid disinfectant traps protect vacuum lines.
  • It is prohibited to keep animals and plants in laboratories that are not related to the research conducted.
  • A biosafety manual is prepared or adopted.

Containment equipment:

  • All classes of biosafety cabinets, physical and personal protective equipment should be present while performing activities having the potential to cause exposure to infectious aerosols. 
  • These include masks, gloves, special protective clothing, respirators, centrifuge safety cups, containment caging for animals, and sealed centrifuge rotors.

Laboratory facilities:

In addition to the facilities mentioned in Biosafety level 1, it also includes:

  • Within the building, the laboratory is separated from areas where the flow of traffic is unrestricted.
  • A sink, which can be operated with an elbow, foot, or automatic, should be placed near the lab exit door to wash hands.
  • Access doors to the laboratory or containment module are self-closing.
  • Class I and Class II Biological safety cabinets with HEPA-filtered exhaust air are vented to the outdoors or through the building’s exhaust system.

Biosafety Level 4

The level of safety procedures and equipment are applicable when labs work with agents that can cause life-threatening diseases, such as the Lassa fever virus[2].

Standard microbiological practices:

  • It includes all standard practices as mentioned in biosafety level 1.

Special practices:

In addition to practices mentioned in Biosafety Level 3:

  • While removing viable biological material from a class III biosafety cabinet to the outside lab, it should be placed in a sealed primary container followed by a sealed secondary container and removed through a disinfectant dunk tank, fumigation chamber, or an airlock designed for this purpose.
  • Facility or individual laboratory room access is restricted to those whose presence is necessary for program or support purposes.
  • Lab personnel is only permitted to enter and exit the facility through the clothing change and shower rooms (each time, a shower is required).
  • The laboratory keeps a report of workplace accidents, employee absences, and potential illnesses associated with the lab.

Containment equipment:

  • A Class III biosafety cabinet is required to perform the procedures. But Class I and Class II biosafety cabinets are also used in combination with one-piece positive-pressure personnel suits ventilated by a life support system. 

Laboratory facilities:

In addition to facilities mentioned in biosafety level 3:

  • Maximum containment facilities are either separate buildings or delineated and isolated areas inside buildings.
  • Facility interiors, such as light fixtures, air ducts, and utility pipes are designed to minimize dust accumulation on horizontal surfaces.
  • Central vacuum systems do not serve areas outside the facility.
  • Before being released from the maximum containment facility, liquid effluents from laboratory sinks, biological safety cabinets, floors, and autoclave chambers are decontaminated by heat treatment.
  •  The facility may include a specially designed suiting area.

To learn all about the facilities, equipment, and special practices of microbiology labs, refer to the materials mentioned in the reference section.


Microbiology laboratories dealing with infectious agents that may pose a threat to laboratory personnel require biosafety measures. These measures include information on standard microbiological practices and procedures, safety equipment, and biosafety facilities.

However, not all microbes possess the same level of threat to humans after their exposure. Therefore, according to the level of danger posed to the public by an infectious agent, four types of biosafety levels are created for the safety of lab personnel, the community, and the environment. According to the levels of their biosafety, the labs are ordered as: Biosafety Level 1, Biosafety Level 2, Biosafety Level 3, and Biosafety Level 4.

Considering the history of people contracting diseases, safety measures are a must in microbial labs. And following these rules, will not only help the people working in labs, but also the people around them, and the whole community.


  1. Biosafety Practices and Procedures for the Microbiology Laboratory. Retrieved from
  2. National Research Council (US) Committee on Hazardous Biological Substances in the Laboratory. Biosafety In The Laboratory: Prudent Practices for the Handling and Disposal of Infectious Materials. Washington (DC): National Academies Press (US); 1989. Appendix A, Biosafety in Microbiological and Biomedical Laboratories. Available from: