Laminar Flow Hood / Cabinet – Principle, Types, Parts, Procedure, Applications & Precautions

Laminar Flow Hood / Cabinet – Principle, Types, Parts, Procedure, Applications & Precautions

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Introduction to Laminar Flow Hood

  • A Laminar Flow Hood (also called Laminar Flow Cabinet) is a special enclosed workstation designed to maintain a contamination-free environment in laboratories.
  • It works by using filters and controlled airflow to remove dust, microbes, and unwanted particles, making the workbench sterile.
  • This cabinet is widely used in microbiology, biotechnology, pharmaceuticals, plant tissue culture, and electronics industries.
  • It is most useful for processes like aseptic media transfer, culture plate pouring, and handling contamination-sensitive materials.

* Important Note: A Laminar Flow Cabinet only protects the sample from contamination, not the user. This is the main difference between a Laminar Flow Cabinet and a Biosafety Cabinet.

Laminar Flow Hood
Figure: Laminar Flow Hood

Principle of Laminar Flow Hood

The working principle of a Laminar Flow Cabinet is based on laminar airflow.

  • Laminar Airflow = smooth, uniform flow of air in a single direction, either vertical (top to bottom) or horizontal (back to front).
  • The air passes through HEPA filters (High-Efficiency Particulate Air filters), which remove dust, bacteria, fungi, and other contaminants.
  • The filtered air is then directed across the workbench, creating a sterile working environment.
  • Constant positive air pressure is maintained inside the cabinet to prevent contaminated air from entering from outside.

In short: Air → Pre-filter → Blower → HEPA Filter → Sterile air flows over workspace.

Working of Laminar Flow Hood; Principle of Laminar Flow Hood
Figure: Working of Laminar Flow Hood

Parts of a Laminar Flow Hood

A Laminar Flow Cabinet is made up of several key parts:

1. Cabinet Structure

  • Made of stainless steel to avoid rust and minimize contamination.
  • Has a glass shield in front for safety. Some models have full front glass, while others have hand openings.

2. Work Station

  • The flat surface inside the cabinet where work is performed.
  • Made of stainless steel for easy cleaning and sterilization.

3. Filter Pad / Pre-Filter

  • Located at the top of the cabinet.
  • Removes larger dust particles before air enters HEPA filters.

4. Fan / Blower

  • Pulls air inside and pushes it towards the filters.
  • Maintains proper airflow direction (vertical or horizontal).

5. HEPA Filter

  • The most important component.
  • Removes 99.97% of particles ≥0.3 microns in size.
  • Ensures that air reaching the workbench is sterile.

6. UV Lamp (Optional)

  • Sterilizes the cabinet before and after use.
  • Must be switched on 15 minutes before use to disinfect.
  • Must be turned off before starting work to avoid harm to the user.

7. Fluorescent Lamp

  • Provides visible light during operation.

Working of Laminar Flow Hood (Step-by-Step)

  1. Air Intake → External air enters through a pre-filter.
  2. Air Blowing → The fan/blower pushes air towards the HEPA filter.
  3. Filtration → HEPA filter removes microbes and particles.
  4. Sterile Air Flow → Clean air flows uniformly (horizontal or vertical) over the workbench.
  5. Positive Pressure → Prevents entry of contaminated outside air.
  6. Exhaust → Sterile air finally leaves towards the operator’s side or downward, depending on type.

Procedure for Using a Laminar Flow Hood

Before Starting Work:

  • Check cabinet for materials sensitive to UV light.
  • Close the glass shield and switch on the UV lamp for 15 minutes to sterilize the interior.
  • After sterilization, switch off UV lamp and wait 10 minutes.
  • Turn on the airflow (blower) at least 5 minutes before use.
  • Wipe the workbench with 70% alcohol or disinfectant.

During Work:

  • Switch on fluorescent lamp for visibility.
  • Open the shield and perform experiments inside the sterile area.
  • Avoid blocking airflow with hands or unnecessary objects.

After Work:

  • Switch off airflow and fluorescent lamp.
  • Close the glass shield.
  • Run UV lamp again for 15 minutes (optional, for sterilization).

Types of Laminar Flow Hood

There are mainly two types of Laminar Flow Hoods based on airflow direction:

1. Vertical Laminar Flow Cabinet

  • Air flows from top to bottom.
  • Requires less floor space.
  • Safer because air does not blow directly at the operator.
  • Commonly used in microbiology and pharmaceutical labs.

2. Horizontal Laminar Flow Cabinet

  • Air flows from back of cabinet towards the operator.
  • Provides constant airflow across the workspace.
  • Easier access to materials but less safe for operator (air hits directly).
  • Used where sample sterility is more important than operator safety.

Uses of Laminar Flow Hood

Laminar Flow Cabinets are widely used in science and industry:

  1. Microbiology & Biotechnology
    • Plant tissue culture.
    • Handling of microbial cultures.
    • Plate pouring and aseptic media transfers.
  2. Pharmaceutical Industry
    • Sterile drug preparation.
    • Quality control testing.
  3. Electronics Industry
    • Assembly of sensitive electronic devices that require dust-free conditions.
  4. Research Laboratories
    • Preparation of sterile solutions.
    • Handling DNA, RNA, and protein samples.
  5. Educational Use
    • Training students in aseptic techniques.

Precautions While Using Laminar Flow Hood

  • Never operate the UV lamp and airflow at the same time.
  • Do not perform work while UV light is on.
  • Always wear lab coat and gloves.
  • Do not overcrowd the workstation with unnecessary items.
  • Disinfect the working surface before and after use.
  • Regularly check and replace HEPA filters.

Advantages of Laminar Flow Cabinet

  • Provides sterile workspace for contamination-sensitive processes.
  • Easy to operate and maintain.
  • Protects samples effectively.
  • Widely available in different sizes and designs.

Limitations of Laminar Flow Cabinet

  • Protects only the sample, not the user.
  • Airflow may disturb lightweight materials like papers or powders.
  • Requires regular maintenance of filters.
  • Not suitable for handling pathogenic microorganisms (Biosafety Cabinet is needed).

FAQs on Laminar Flow Hood

Q1. What is the main purpose of a laminar flow cabinet?
Ans: To provide a sterile environment for working with contamination-sensitive materials.

Q2. How is it different from a biosafety cabinet?
Ans: Laminar Flow Cabinet protects only the sample, while Biosafety Cabinet protects both sample and user.

Q3. How often should HEPA filters be replaced?
Ans: Typically once every 6–12 months depending on usage.

Q4. Can we use it for pathogenic microbes?
Ans: No, it is unsafe. Biosafety cabinets should be used instead.

Q5. Why is UV lamp used in laminar flow hood?
Ans: To sterilize the cabinet before and after use by killing microbes.

Conclusion

The Laminar Flow Hood/Cabinet is an essential laboratory equipment that ensures a contamination-free environment. It is widely used in microbiology, biotechnology, pharmaceuticals, electronics, and educational labs.

By understanding its principle, parts, types, procedure, applications, advantages, and precautions, students and researchers can effectively use it for aseptic operations.

* Always remember: Laminar Flow Cabinets protect the sample, but not the operator – so safety precautions must be strictly followed.

References and Sources

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