Biological Safety Cabinets (BSCs) – Definition, Classes, Working, Applications, Advantages & Precautions

Table of Contents

Introduction to Biological Safety Cabinets

Biological Safety Cabinets (BSCs), also called biosafety cabinets or microbiological safety cabinets, are enclosed ventilated laboratory workspaces designed to protect personnel, samples, and the environment from biohazardous materials.
They are essential in labs dealing with pathogens, infectious agents, and potentially harmful biological samples.
BSCs are sometimes confused with laminar flow hoods, but there is an important difference:
- Laminar flow hoods protect only the sample (not personnel or the environment).
- Biological Safety Cabinets provide triple protection – to the user, the sample, and the laboratory environment.
A BSC is often referred to as a tissue culture hood, especially in cell biology and microbiology labs.

In short: A Biological Safety Cabinet is a primary barrier against infectious aerosols, droplets, and biohazardous agents, ensuring safe laboratory practices.

Principle of Biological Safety Cabinets

BSCs operate on the principle of airflow control and HEPA filtration.
Airflow:
- A strong air curtain prevents aerosols from escaping the cabinet.
- Air inside the cabinet is continuously recirculated through HEPA (High-Efficiency Particulate Air) filters, ensuring sterility.
HEPA Filtration:
- Removes 99.97% of airborne particles ≥ 0.3 µm, including bacteria, spores, and many viruses.
- Does not remove gases or volatile chemicals.

Thus, the BSC functions as an aerosol containment system, protecting people, samples, and the environment.

Levels of Protection Offered by BSCs

Personnel Protection – Users are shielded from aerosols via HEPA-filtered exhaust and air barriers.
Sample/Product Protection – Recirculating HEPA-filtered air prevents contamination of cultures and experiments.
Environmental Protection – Exhaust air is filtered before release, preventing spread of pathogens to the lab or outside environment.

Classes of Biological Safety Cabinets

There are three major classes of BSCs, each providing a different level of safety:

Class I Biosafety Cabinet

Class I Biological Safety Cabinets — **Figure :** Class I Biosafety Cabinet

Protection: Personnel + Environment (NOT the sample).
Airflow: Open front; inward airflow at ~0.38 m/s → passes over workspace → HEPA-filtered → exhausted outside or back into lab.
Ducting: Can be ducted (to external exhaust) or unducted (recirculating).
Best for: Handling low- and moderate-risk pathogens (RG1–RG3), but not sterile cultures.
Features:
- Open front sash
- Exhaust plenum
- HEPA filter
Uses:
- Cage dumping in animal facilities
- Handling cultures producing aerosols
- Centrifuge housing and fermenters

Class II Biosafety Cabinet

Protection: Personnel + Product + Environment (triple protection).
Airflow: Uses laminar airflow + HEPA filtration.
Applications: Widely used in clinical, pharmaceutical, hospital, and research labs for handling pathogens in Risk Groups 2–3.
Types of Class II BSCs:
1. Type A1: 70% recirculated air, 30% exhausted back into the room.
  - Not suitable for toxic chemicals.
2. Type A2: 70% recirculated, 30% exhausted via HEPA filter.
  - Can handle radioactive nucleotides and some chemicals.
3. Type B1: 30% recirculated, 70% exhausted externally.
  - Useful for moderate-risk chemicals and biohazards.
4. Type B2: 100% air exhausted externally (no recirculation).
  - Best for toxic chemicals + infectious materials.
5. Type C1: Hybrid – can function as Type A (recirculating) or Type B (exhausting) depending on lab requirements.

Class II BSCs are the most common choice in research labs due to their versatility and safety.

Class II Type A1 Biological Safety Cabinets — **Figure:** Class II Type A1 Biosafety Cabinet

Class II Type A2 Biological Safety Cabinets — **Figure:** Class II Type A2 Biosafety Cabinet

Class II Type B1 Biological Safety Cabinets — **Figure:** Class II Type B1 Biosafety Cabinet. Image Source: Biosafety in Microbiological and Biomedical Laboratories. CDC.

Class II Type B2 Biological Safety Cabinets — **Figure:** Class II Type B2 Biosafety Cabinet. Image Source: Biosafety in Microbiological and Biomedical Laboratories. CDC.

Class II Type C1 Biological Safety Cabinets — **Figure:** Class II Type C1- Not Connected to Exhaust System. Image Source: Biosafety in Microbiological and Biomedical Laboratories. CDC.

Class III Biosafety Cabinet

Protection: Maximum protection (Personnel + Product + Environment).
Design: Gas-tight, fully enclosed “glove box” system.
Operation: Samples handled through attached rubber gloves.
Airflow: Double HEPA filters for exhaust; negative pressure to prevent leaks.
Applications: Used with BSL-4 pathogens (e.g., Ebola, Marburg viruses).
Features:
- Double-ended autoclave for material transfer
- Chemical dunk tanks
- Glove ports
Uses:
- Handling highly infectious or lethal pathogens
- Work with carcinogens, emerging diseases, and dangerous viruses

Class III Biological Safety Cabinets — **Figure:** Class III Biosafety Cabinet

Operating Procedures of a Biological Safety Cabinet

Preparation
- Switch off UV light, switch on fluorescent lamp.
- Start blower, purge for 5–10 minutes.
- Disinfect all interior surfaces.
Loading Materials
- Place only required materials inside.
- Keep hazardous waste container at the rear.
- Arrange sterile and contaminated items separately.
During Work
- Wear PPE (lab coat, gloves, mask).
- Minimize arm movements to avoid airflow disruption.
- Work at least 4 inches inside the cabinet.
- Do not block front or rear grilles.
After Work
- Allow air purge.
- Remove contaminated materials safely.
- Disinfect interior surfaces.
- Switch off blower, turn on UV light for sterilization.

Applications of Biological Safety Cabinets

Opening containers under non-ambient pressure
Handling infectious animal tissues or fluids
Necropsy of infected animals
Inoculation of animals (e.g., intranasal studies)
Cell culture and tissue culture experiments
Sonication, blending, vortex mixing of samples
Centrifugation and specimen separation
Working with potentially infectious aerosols

BSCs are mandatory in microbiology, virology, immunology, tissue culture, and clinical labs where biohazards are present.

Advantages of Biological Safety Cabinets

Protects user, product, and environment.
Removes infectious aerosols.
Allows safe research on Risk Groups 1–4 pathogens.
Reduces contamination in tissue culture experiments.
Class III provides maximum containment for lethal pathogens.

Limitations of Biological Safety Cabinets

Expensive to purchase and maintain.
Requires regular certification and professional servicing.
Cannot eliminate toxic gases or volatile chemicals (except Class II B2 and Class III).
Improper use (blocking vents, sudden movements) reduces efficiency.
Class I and II still have small exposure risk through front opening.

Precautions While Using BSCs

Always wear PPE (lab coat, gloves, safety glasses).
Place all materials inside before starting work.
Never switch on UV light during operation (eye/skin damage).
Do not use open flames (Bunsen burners) inside.
Avoid quick hand movements.
Do not block air vents.
Regularly clean and disinfect surfaces.
Schedule annual certification by trained personnel.

Examples of Biological Safety Cabinets

Biobase Class I (BBS, BYKG series)
- LED display, HEPA filters (99.999% efficiency at 0.3 µm).
Bioevopeak BSC-IIA2-2J
- Ergonomic design, high security, front window design.
UNO Class II (IF-MVK 183)
- Protects user + product + environment, minimizes cross-contamination.
LAMSYSTEMS Class III (BMB-III “Laminar-S”)
- Sealed glove box, HEPA filtration, optional exhaust connection.

FAQs on Biological Safety Cabinets

Q1. What is a Biological Safety Cabinet (BSC)?
Ans: A Biological Safety Cabinet (BSC) is a ventilated laboratory workspace that provides protection to personnel, the environment, and the samples from biohazards by controlling airflow and filtering it through HEPA filters.

Q2. What is the principle of a Biological Safety Cabinet?
Ans: BSCs work on the principle of airflow containment and HEPA filtration. Air is drawn into the cabinet, filtered to remove microorganisms and particles, and recirculated or exhausted safely.

Q3. What is the difference between a laminar flow hood and a BSC?
Ans:

Laminar Flow Hood: Protects only the sample from contamination.
Biological Safety Cabinet: Protects the sample, user, and environment simultaneously.

Q4. What are the main classes of Biological Safety Cabinets?
Ans: There are three main classes:

Class I – Protects personnel and environment (not the sample).
Class II – Protects personnel, environment, and sample (most common in labs).
Class III – Maximum protection, used for highly infectious BSL-4 pathogens.

Q5. Which class of BSC is most commonly used?
Ans: Class II BSCs are the most widely used because they offer triple protection and are suitable for Risk Group 2 and 3 pathogens.

Q6. Can BSCs remove viruses?
Ans: Yes. BSCs use HEPA filters that remove 99.97% of particles ≥ 0.3 µm, including most bacteria and viruses. However, they cannot remove toxic gases or volatile chemicals unless specially designed (Class II B2 or Class III).

Q7. Which BSC is used for handling Ebola virus or BSL-4 pathogens?
Ans: Class III BSCs (glove box cabinets) are used for handling extremely dangerous agents such as Ebola, Marburg virus, and other BSL-4 pathogens.

Q8. How often should Biological Safety Cabinets be certified?
Ans: At least once every year or whenever the cabinet is moved to a new location. Certification ensures filters and airflow are functioning correctly.

Q9. Can I use an open flame (Bunsen burner) inside a BSC?
Ans: No. Open flames disturb airflow and may cause accidents. Instead, use electric sterilizers or micro-incinerators inside BSCs.

Q10. What is the lifespan of HEPA filters in BSCs?
Typically 3–5 years, depending on usage and environment. They should be inspected regularly and replaced by certified technicians.

Q11. Why should UV light not be used while working in a BSC?
Ans: UV light is harmful to skin and eyes. It should only be used for sterilization before or after work, never during operation.

Q12. Can BSCs be used with chemicals?
Ans: Only Class II Type B2 and Class III BSCs can safely handle volatile chemicals or toxic gases. Standard Class I and II (Type A) BSCs are not designed for chemical hazards.

Q13. How do BSCs protect the user?
Ans: By creating an air curtain at the front opening and filtering exhaust air through HEPA filters, preventing aerosols and pathogens from escaping.

Q14. What is the difference between Class II A2 and Class II B2 BSCs?
Ans:

Class II A2: 70% air recirculated, 30% exhausted; suitable for most microbiological work.
Class II B2: 100% exhaust; suitable for work with infectious agents + toxic chemicals.

Q15. Are BSCs mandatory in microbiology labs?
Ans: Yes, for labs handling Risk Group 2 or higher pathogens. They are part of biosafety regulations in hospitals, research centers, and pharmaceutical labs.

Conclusion

Biological Safety Cabinets (BSCs) are essential laboratory equipment that provide triple protection – for the operator, the samples, and the environment. With three classes (I, II, and III), they cater to different biosafety levels and laboratory needs.

They play a critical role in microbiology, biotechnology, pharmaceuticals, and clinical research, ensuring that hazardous pathogens are handled safely. Despite their high cost and need for maintenance, their life-saving role in biosafety cannot be overstated.

In short: A BSC is a must-have biosafety tool for any laboratory working with infectious or hazardous biological materials

References

https://labsafety.gwu.edu/biosafety-cabinets
https://ehs.mit.edu/biological-program/biological-biosafety-cabinets/
https://microbenotes.com/biological-safety-cabinets-classes-examples/
https://www.labogene.com/Biological-Safety-Cabinets
https://www.laboratory-supply.net/blog/aseptic-containment-isolator-vs-biological-safety-cabinet/
https://blink.ucsd.edu/safety/research-lab/biosafety/containment/bsc/usage.html#Take-precautions-before-beginni
https://microbeonline.com/biological-safety-cabinet-bsc-types-working-mechanism/